French prosecutors on Monday opened a preliminary investigation into accusations that disgraced ex-IMF chief Dominique Strauss-Kahn took part in a gang rape in the United States.

Prosecutors in Lille, where Strauss-Kahn and three others have been charged in a pimping case, said the probe centred on an incident "that could be described as gang rape" that took place in Washington, DC in December 2010.

A senior U.S. official warned North Korea Monday against conducting another nuclear test, saying it would be a "serious mistake" that would incur more sanctions and further isolation.

"I think it will be a serious miscalculation and mistake if North Korea were to engage in a nuclear test," Glyn Davies, U.S. special envoy for North Korea policy, told reporters.

China expressed Saturday its "firm opposition" to a Pentagon report that said Beijing was carrying out aggressive cyber espionage as part of a steady build-up of its military power, state media said.

Foreign ministry spokesman Hong Lei said "China's justified and normal military development" had been unjustly criticized in the annual report, which was released on Friday, according to the Xinhua news agency.

Russia's non-intervention stance on Syria remained unchanged on Saturday as G8 leaders looked to hammer out a joint declaration to put greater pressure on President Bashar Assad's regime.

"There cannot be any change of regime through force," the Kremlin's Africa envoy, Mikhail Margelov said, adding that G8 leaders meeting at Camp David had yet to agree on the Syria part of their final summit declaration.

Blind Chinese activist Chen Guangcheng was on a plane headed for the United States with his family Saturday, U.S. officials said, ending weeks of uncertainty for the now world-famous rights campaigner.

Chen's escape from house arrest, turning up at the U.S. embassy before leaving again, also caused a major diplomatic rift between Washington and Beijing, with China telling the U.S. to keep its nose out of Chinese affairs.

France's President Francois Hollande used his White House debut Friday to restate his intention to get French combat troops home from Afghanistan this year -- breaking with NATO's 2014 schedule.

Hollande met U.S. President Barack Obama for the first time since taking office three days ago, ahead of a testing weekend of international summits, with G8 leaders at Camp David and NATO chiefs at a 61-nation gathering in Chicago.

A Japanese bank has halted transactions by the Iranian government after a U.S. court ordered a $2.6 billion asset freeze over the 1983 bombing of U.S. barracks in Beirut, a bank spokesman said Thursday.

"It is true that we have received the order from the U.S. court," to freeze $2.6 billion of assets, a spokesman for the Bank of Tokyo-Mitsubishi UFJ told Agence France Presse, declining to give details on the value of Iranian holdings at the bank.

The United States and 18 other countries have started in Jordan what was described as the largest military exercises in the Middle East in 10 years, focusing on "irregular warfare," top officers said on Tuesday.

"Yesterday we began to apply the skills that we have developed over the last weeks in an irregular warfare scenario ... They will last for approximately the coming two weeks," Major General Ken Tovo, head of the U.S. Special Operations Forces, told reporters in Amman.

Pakistan on Tuesday looked poised to end a nearly six-month blockade of NATO ground supply routes into Afghanistan, succumbing to a key demand of the West ahead of a summit in Chicago next week.

Islamabad shut its Afghan border crossings to NATO supplies after U.S. air strikes killed 24 soldiers last November, provoking a new crisis in ties on top of the outcry from the U.S. raid that killed Osama bin Laden in May that year.

Ron Paul, the U.S. congressman who led a stubbornly persistent presidential bid against presumptive Republican nominee Mitt Romney and other rivals, said Monday he is suspending active campaigning.

Paul said in a statement he will "no longer spend resources campaigning in primaries," opting instead to work on amassing delegates to the party's national convention, even though his chances of winning the nomination are virtually nil.