(Reuters) - Facebook stock sank on Monday in the first day of trading without the full support of the company's underwriters, leaving some investors down nearly 25 percent from where they were Friday afternoon. Facebook's debut was beset by problems, so much so that Nasdaq said on Monday it was changing its IPO procedures. That may comfort companies considering a listing but does little for Facebook, whose lead underwriter Morgan Stanley had to step in and defend the $38 offering price on the open market. Without that same level of defense, its shares fell $4.64 to $33. ...

Stocks rose Monday morning as investors latched onto a survey suggesting that economists are more optimistic about housing and unemployment.

WASHINGTON (Reuters) - Gregory Jaczko, the chairman of the U.S. Nuclear Regulatory Commission, announced on Monday he would resign from the post after a year of intense criticism of his management tactics. "After an incredibly productive three years as Chairman, I have decided this is the appropriate time to continue my efforts to ensure public safety in a different forum," Jaczko said in a statement. (Reporting by Roberta Rampton)

SANAA (Reuters) - A man with explosives strapped under his army uniform killed more than 90 people in the Yemeni capital Sanaa on Monday when he blew himself up in the midst of a military parade rehearsal, the defense ministry said. The ministry also said 222 people were wounded in the attack. (Reporting by Mohammed Ghobari; Writing by Isabel Coles; Editing by Louise Ireland)

SANAA (Reuters) - A man with explosives strapped under his army uniform killed more than 90 people in the Yemeni capital Sanaa on Monday when he blew himself up in the midst of a military parade rehearsal, the defense ministry said. The ministry also said 222 people were wounded in the attack. (Reporting by Mohammed Ghobari; Writing by Isabel Coles; Editing by Louise Ireland)

VIENNA/DUBAI (Reuters) - The U.N. nuclear watchdog chief held rare talks in Tehran on Monday after voicing hope for a deal to investigate suspected atomic bomb research - a gesture Iran might make to try to get international sanctions relaxed and deflect threats of war. International Atomic Energy Agency Director-General Yukiya Amano began discussions with the head of Iran's nuclear energy organization, Fereydoun Abbasi-Davani, a few hours after his pre-dawn arrival, according to ISNA news agency. ...

VIENNA/DUBAI (Reuters) - The U.N. nuclear watchdog chief held rare talks in Tehran on Monday after voicing hope for a deal to investigate suspected atomic bomb research - a gesture Iran might make to try to get international sanctions relaxed and deflect threats of war. International Atomic Energy Agency Director-General Yukiya Amano began discussions with the head of Iran's nuclear energy organization, Fereydoun Abbasi-Davani, a few hours after his pre-dawn arrival, according to ISNA news agency. ...

NEW YORK (Reuters) - JPMorgan Chase & Co Chief Executive Officer Jamie Dimon said on Monday that the bank had suspended repurchases of its stock, but is maintaining its dividend, while working down losing trades in credit derivatives. Shares of JPMorgan were down 1 percent at $33.13 in morning trading after Dimon started speaking at the Deutsche Bank Securities Global Financial Services Investor Conference in New York. The bank announced on May 10 that it had lost at least $2 billion mishandling a portfolio of credit derivatives. JPMorgan won permission from the U.S. ...

MOSCOW (Reuters) - Russian President Vladimir Putin unveiled a government dominated by loyalists on Monday, tightening his grip on the economy and national security after protests, and limiting Prime Minister Dmitry Medvedev's ability to pursue market reforms. Putin, 59, opted for continuity by retaining his ally Igor Shuvalov as first deputy prime minister in charge of economic policy, while Igor Sechin will remain his energy chief in a role outside the government. ...

NEW YORK (Reuters) - Stocks edged up on Monday from their worst weekly decline for the year as world leaders expressed support for Greece to stay in the euro zone, but gains were limited as shares of Facebook dropped more than 13 percent shortly after the open. Facebook Inc's shares fell below their $38 issue price as support from underwriters of the initial public offering dissipated after its Friday debut. The stock dropped over $5 to hit a session low of $33.00 in early trading. ...

Global stocks rose modestly on Monday, though gains were limited by concerns that leaders from the Group of Eight most powerful countries had failed to provide a concrete plan to ease the eurozone debt crisis.

SHANGHAI/NEW YORK (Reuters) - Chinese Internet entrepreneur Jack Ma is buying back up to half of a 40 percent stake in his Alibaba Group from Yahoo Inc for $7.1 billion, in a deal that moves the Chinese e-commerce leader closer to a public listing. Under the agreement, Yahoo will sell half its stake in Alibaba for at least $6.3 billion in cash and up to $800 million in new Alibaba preferred stock. ...

SHANGHAI/NEW YORK (Reuters) - Chinese Internet entrepreneur Jack Ma is buying back up to half of a 40 percent stake in his Alibaba Group from Yahoo Inc for $7.1 billion, in a deal that moves the Chinese e-commerce leader closer to a public listing. Under the agreement, Yahoo will sell half its stake in Alibaba for at least $6.3 billion in cash and up to $800 million in new Alibaba preferred stock. ...

NEW YORK (Reuters) - Barely a day went by at the insider-trading trial of multimillionaire hedge-fund founder Raj Rajaratnam a year ago without mention of Rajat Gupta, a boldface name in business and charity circles. On Monday in the same federal court in New York, it will be Gupta's turn to go on trial. The former Goldman Sachs Group Inc and Procter & Gamble board member is accused of leaking stock secrets to Rajaratnam, his erstwhile friend and business associate who was convicted and is now in prison. ...

Port-au-Prince (Reuters) - Haitian authorities on Sunday announced the arrest of 59 uniformed former soldiers and several alleged supporters who staged a series of protests on Friday and Saturday calling for the return of the nation's disbanded army. The soldiers and their allies were charged with forming a rogue army and repeatedly violating government orders to remove their uniforms and lay down their weapons, officials said. In 1995, President Jean-Bertrand Aristide dismantled the Haitian army, which had staged numerous coups and committed human rights abuses. ...

Port-au-Prince (Reuters) - Haitian authorities on Sunday announced the arrest of 59 uniformed former soldiers and several alleged supporters who staged a series of protests on Friday and Saturday calling for the return of the nation's disbanded army. The soldiers and their allies were charged with forming a rogue army and repeatedly violating government orders to remove their uniforms and lay down their weapons, officials said. In 1995, President Jean-Bertrand Aristide dismantled the Haitian army, which had staged numerous coups and committed human rights abuses. ...

TRIPOLI (Reuters) - - The Libyan convicted of the 1988 bombing of a PanAm flight over Lockerbie was buried on Monday in a quiet family ceremony, ignored by most Libyans keen to forget the international controversy that surrounded Abdel Basset al-Megrahi in life. Megrahi, who always said he was not responsible for bringing down the jumbo jet on the Scottish town and killing 270 people, died in his bed in Tripoli on Sunday surrounded by family. His release from jail in 2009 caused controversy in Britain and the United States, where most victims were from. ...

(Reuters) - Lowe's Cos Inc , the world's No. 2 home improvement chain, cut its fiscal-year earnings outlook and said demand slowed toward the end of the traditionally strong first quarter, sending its shares down nearly 10 percent. Lowe's forecast came just days after larger rival Home Depot Inc missed Wall Street's quarterly sales estimates as demand weakened in April following a jump in home improvement projects earlier in the year because of a warm winter. ...

PARIS (Reuters) - The fate of a struggling small French mortgage lender will be the first banking test for President Francois Hollande, as he attempts to deliver on campaign promises of economic growth and tougher financial regulation. Policymakers and bankers are scrambling to avert an outright collapse of Credit Immobilier de France, whose future was thrown into doubt after Moody's cut its standalone bank financial strength rating and said it was no longer viable without support. ...

PARIS (Reuters) - The fate of a struggling small French mortgage lender will be the first banking test for President Francois Hollande, as he attempts to deliver on campaign promises of economic growth and tougher financial regulation. Policymakers and bankers are scrambling to avert an outright collapse of Credit Immobilier de France, whose future was thrown into doubt after Moody's cut its standalone bank financial strength rating and said it was no longer viable without support. ...

VIENNA/DUBAI (Reuters) - The U.N. nuclear watchdog chief held rare talks in Tehran on Monday after voicing hope for a deal to investigate suspected atomic bomb research - a gesture Iran might make to try to get international sanctions relaxed and deflect threats of war. International Atomic Energy Agency Director-General Yukiya Amano began discussions with the head of Iran's nuclear energy organization, Fereydoun Abbasi-Davani, a few hours after his pre-dawn arrival, according to ISNA news agency. ...

VIENNA/DUBAI (Reuters) - The U.N. nuclear watchdog chief held rare talks in Tehran on Monday after voicing hope for a deal to investigate suspected atomic bomb research - a gesture Iran might make to try to get international sanctions relaxed and deflect threats of war. International Atomic Energy Agency Director-General Yukiya Amano began discussions with the head of Iran's nuclear energy organization, Fereydoun Abbasi-Davani, a few hours after his pre-dawn arrival, according to ISNA news agency. ...

BERLIN (Reuters) - Europe's fiscal pact must not be renegotiated or softened but could be complemented by growth-enhancing measures, European Central Bank Executive Board member Joerg Asmussen said on Monday. Asmussen also stressed that the ECB's non-standard measures - introduced to fight the debt crisis - were of a temporary nature and could be withdrawn any time if inflation risks emerged. There is a growing push in the euro zone, led by newly elected French President Francois Hollande, to do more to stimulate growth and not just focus on reducing deficits. ...