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.
The Syrian opposition has said the president's forces killed as many as 1,300 people when they unleased chemical weapons east and southwest of Damascus in attacks on Wednesday.
UN Under Secretary General Angela Kane was in the Syrian capital on Saturday for talks aimed at establishing the terms of an inquiry into the alleged attacks.
A team of UN arms inspectors has been in Syria since August 18 to probe three other sites, but the government has yet to say if it will let them inspect the latest allegations.
"We ask that the UN team that is there can be deployed very quickly and make the necessary inspections," Fabius said.
"The information which we have shows that this chemical massacre is of such gravity that it obviously cannot pass without a strong reaction," he added.
The Syrian government has strongly denied accusations it carried out the attacks.
Speaking later Saturday to journalists in Jerusalem, Fabius said regime allegations that rebels used chemical weapons were not supported by evidence.
"The indications which we have do not point in that direction," Fabius said. "This makes it all more the more urgent that the UN mission is able to investigate immediately and without restraint."
Fabius arrived early Saturday on a visit to Israel and the Palestinian territories aimed at encouraging resumed peace talks, his office said.
He met Palestinian president Mahmud Abbas and prime minister Rami Hamdallah at their headquarters in Ramallah.
In Israel on Sunday, he will meet with President Shimon Peres, Prime Minister Benjamin Netanyahu and Justice Minister Tzipi Livni, Israel's negotiator in the US-brokered talks.