French Foreign Minister Laurent Fabius said on Saturday that all indications show that Syria's government was behind a "chemical massacre" near Damascus that the opposition claims killed hundreds.
"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.
Opponents of Bashar al-Assad said the president's forces killed 1,300 people when they unleased chemical weapons east and southwest of Damascus in the attacks on Wednesday.
UN Under Secretary General Angela Kane arrived in the Syrian capital on Saturday for talks aimed at establishing the terms of an enquiry into the alleged attacks, an AFP journalist said.
"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.
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The Syrian government has strongly denied accusations it carried out the attacks, but so far it has not said whether it will let UN inspectors visit the sites.
Fabius arrived early Saturday on a visit to Israel and the Palestinian territories aimed at encouraging recently resumed peace talks, his office said.
He met Palestinian president Mahmud Abbas and prime minister Rami Hamdallah at their headquarters in the West Bank city of Ramallah on Saturday.
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 talks.
"This visit will be an opportunity for the minister to encourage these Palestinian and Israeli negotiators to continue direct negotiations in favour of peace," French foreign ministry deputy spokesman Vincent Floreani said.
The French side would also express "determination to support these efforts," he added.
Israeli and Palestinian negotiators formally resumed direct peace talks earlier this month after a hiatus of nearly three years, thanks to an intense bout of shuttle diplomacy by US Secretary of State John Kerry.
The Palestinians said Friday they have "serious doubts" about Israel's commitment to the peace talks, but they remain committed to taking part in the negotiations.
"We do not have high expectations of the negotiations so far because we know in advance the official position of the Israeli government," foreign minister Riyad al-Malki said on visit to Quito, Ecuador.