U.S. President Barack Obama met with security aides Saturday to discuss a response to Syria's alleged chemical attack after the Pentagon said it was preparing for possible military action.

The meeting came a day after Defense Secretary Chuck Hagel said the military had presented options to Obama and was moving forces into place ahead of any possible decision.

Egypt partially reopened the Rafah crossing with Gaza on Saturday, a Hamas official said, more than a week after it closed the strip's only land passage that bypasses Israel.

Maher Abu Sabha, director general of border crossing for Gaza's Islamist Hamas government, said the terminal opened in the morning and would operate every day for four hours "for humanitarian cases and holders of foreign passports".

Iran, the chief regional ally of Damascus, said on Saturday there is "proof" Syrian rebels used chemical weapons in their conflict with the regime of President Bashar Assad.

"We are very concerned about information regarding the use of chemical weapons in Syria, and we strongly condemn the use of such weapons," foreign ministry spokesman Abbas Araqchi said, quoted by ISNA news agency.

German Chancellor Angela Merkel has criticized Damascus allies China and Russia for blocking a Western-backed U.N. text demanding that inspectors probing chemical weapons use in Syria be given unfettered access.

Her comments were made in an interview with Focus magazine, extracts of which were published on Saturday, even as a top U.N. envoy arrived in Damascus to discuss the terms on an inquiry into the alleged chemical attacks.

French Foreign Minister Laurent Fabius said on Saturday that all indications show the Syrian government was behind a "chemical massacre" near Damascus that the opposition claims killed hundreds of people.

"All the information at our disposal converges to indicate that there was a chemical massacre near Damascus and that the Bashar regime is responsible," Fabius said on a visit to Ramallah in the West Bank.

Syria's opposition denied Saturday charges that rebels had resorted to the use of chemical arms, saying the government was attempting to divert attention from its own use of them.

"The National Coalition totally rejects the lies from the (President Bashar) Assad regime and considers them a desperate bid to divert attention from its repeated crimes and methods against Syrian civilians," the main opposition bloc said.

Baghdad residents held funerals Saturday for victims of a suicide bombing that killed 28 people in a city park, even as authorities pressed operations against militants to stem growing violence.

Authorities have launched a fierce crackdown on militants blamed for a wave of nationwide shootings and blasts that has killed more than 3,600 people this year, but have faced criticism for not addressing the root causes of the violence.

U.S. officials are looking at the air war over Kosovo in the late 1990s as a possible blueprint for strikes on Syria without a UN mandate, the New York Times reported Saturday.

During the 1998-1999 conflict, Russia supported the Yugoslav regime of Slobodan Milosevic, accused of committing atrocities against civilians in Kosovo. But since Russia holds veto power in the UN Security Council, there was no chance of getting a resolution authorizing the use of force against the Yugoslav Republic.

A U.S. photojournalist who escaped from Syrian rebels after seven months in captivity revealed details of his ordeal Friday and spoke of his anguish at leaving a fellow hostage behind.

Matthew Schrier, 35, fled the clutches of a rebel group aligned to al-Qaida in July after being kidnapped while leaving the Syrian city of Aleppo on December 31 last year.

Iranian President Hassan Rowhani on Saturday pointed to the use of chemical weapons in Syria, three days they allegedly killed hundreds of people in attacks near Damascus.

Syria's main opposition group, the National Coalition, accused the government of "massacring" more than 1,300 people in chemical weapons attacks on Wednesday.