Former IMF chief Dominique Strauss-Kahn was freed from French police custody Wednesday after two days of questioning about an alleged prostitution ring but faces a further grilling next month.

A judicial source said Strauss-Kahn, once considered a front-runner to become the next president of France, would be summoned to appear before investigating magistrates on March 28 on charges linked to prostitution and corruption.

Four Bosnian Croats, including a woman, were arrested on Wednesday accused of committing war crimes against Serb civilians at the start of the 1992-1995 war, justice officials said.

The former members of paramilitary forces are suspected of committing war crimes against Serb civilians in a detention camp in May 1992, shortly after the start of the war, the Bosnian war crimes prosecutor's office said.

The U.N. Security Council unanimously agreed Wednesday to increase the African Union force in Somalia from 12,000 to 17,731 troops.

A resolution passed by the 15-nation council gave the African force a tougher mandate to attack Shebab Islamist militants and substantially increased international funding for the military operation.

A packed commuter train slammed into barriers at a railway terminus in the Argentine capital Buenos Aires during rush hour Wednesday, leaving an unknown number of people dead, 550 injured, and dozens trapped in the wreckage.

"The train was full and the impact was tremendous," a passenger identified only as Ezequiel told local television, stating that medics at the scene were overwhelmed.

Russia on Wednesday warned against the use of force to solve the crisis over the Iranian nuclear program, saying an attack would have catastrophic consequences both for the region and global diplomacy.

"The scenario of military action against Iran would be catastrophic for the region and possibly the whole system of international relations," Deputy Foreign Minister Gennady Gatilov told a news conference.

Australian Prime Minister Julia Gillard said she was "disappointed" the man she deposed as leader, Kevin Rudd, had not discussed plans to resign as Foreign Minister or raised his concerns with her.

Rudd resigned his post at a dramatic midnight press conference in Washington, saying he had lost the confidence of Gillard amid speculation he was preparing a leadership challenge and would return home to consider his future.

A Thai court on Wednesday allowed police to continue to detain one of five Iranian suspects in an alleged terror plot that was exposed by an accidental blast in a residential Bangkok neighborhood.

Police Maj. Gen. Piya Uthayo said Mohammad Kharzei, 42, will be held at a Bangkok prison for at least 12 more days. He was arrested on charges of being an accomplice to possession of unlawful explosives and causing explosions that damaged property and harmed other people.

Russia on Wednesday said it could not rule out that the United States would use the U.S. Manas airbase in ex-Soviet Kyrgyzstan for an eventual strike on Iran over its contested nuclear program.

"It cannot be excluded that this site could be used in a potential conflict with Iran," foreign ministry spokesman Alexander Lukashevich told reporters. "We hope that such an apocalyptic scenario will not be realized."

Taiwan's navy will arm its submarines with anti-ship missiles for the first time ever beginning next year, a report said Wednesday, as the island boosts its defense capabilities against rival China.

The Taipei-based United Daily News said the navy, which ordered the U.S.-built Harpoon missiles in 2008, recently test-fired the weapons in the United States, in preparation for installing them on its two Dutch-built submarines.

Iran's supreme leader Ayatollah Ali Khamenei insisted on Wednesday that his country is not seeking an atomic weapon, following an unsuccessful visit to Tehran by U.N. nuclear watchdog officials.

"We are not after an atomic weapon. We want to break the supremacy (of the world powers) that relies on nuclear weapons. God willing, the nation will reach this goal," he told a meeting with Iranian nuclear scientists, according to an official government statement.