An Associated Press photographer saw the members wearing body armour leaving in seven SUVs. It was not clear if the team was headed to the suburb where the alleged attack occurred.
The United States has said that there is little doubt that Assad's regime was responsible for the attack on Aug. 21 in the capital's eastern suburbs. The group Doctors Without Borders said 355 people were killed in an artillery barrage by regime forces Wednesday that included the use of toxic gas.
The Britain-based Syrian Observatory for Human Rights says the eastern suburbs have witnessed a wide army offensive over the last week, but have been relatively quiet since Sunday night.
Mohammed Abdullah, an activist in the eastern suburb of Saqba, said the U.N. is expected to visit the rebel-held area on Monday and they will be under the protection of the Islam Brigade, which has thousands of fighters in the area.
The photographer said U.N. disarmament chief Angela Kane saw them as they left but did not go with them on Monday morning.
Syrian activists and opposition leaders have said that between 322 and 1,300 people were killed in the alleged chemical attack on Wednesday.
Syria said Sunday that a U.N. team could investigate the site but a senior White House official dismissed the deal as "too late to be credible."
Assad told Russia's Izvestia daily that the accusations that his troops used chemicals were responsible were "politically motivated."
"This is nonsense," Assad was quoted as saying in an interview published Monday. "First they level the accusations, and only then they start collecting evidence."
Assad said that attacking such an area with chemical weapons would not make sense for the government as there was no clear front line between regime and rebel forces.
"How can the government use chemical weapons, or any other weapons of mass destruction, in an area where its troops are situated?" he said. "This is not logical. That's why these accusations are politically motivated, and a recent string of victories of the government forces is the reason for it."
With France, Britain, Israel and some U.S. congressmen urging swift military action against Assad's regime if the use of chemical agents is confirmed, the U.N. team's conclusions could have a dramatic impact on the trajectory of the country's civil war.
French Foreign Minister Laurent Fabius said no decision had been made on a military intervention but that any response would be "proportionate."
"It will be negotiated in coming days," Fabius told Europe 1 radio on Monday. He said that the lack of a U.N. blessing was problematic, but that all options remain on the table.
"The only option that I can't imagine would be to do nothing," Fabius said.
Russia, who has been a staunch ally of Syria, said last week that the accusations against Assad could be a bid to get the Security Council to stand by the opposition and to undermine efforts to resolve the conflict by convening a peace conference in Geneva.
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