While there were no immediate reports of injuries, "the car was no longer serviceable," so the inspectors "returned safely back to the government check-point," the United Nations said in a statement in New York, urging the combatants to cooperate with efforts to establish what happened in the attack last Wednesday. "The team will return to the area after replacing the vehicle," the statement said.
There was no independent account of who had opened fire. News reports indicated that the inspectors arrived later in a rebel-held area. Reuters quoted a doctor as saying members of the United Nations team were meeting with physicians and taking samples from survivors of the attack. News agencies reported earlier that the United Nations inspectors had left central Damascus and were traveling to the area on Monday in a convoy of six or seven vehicles escorted by Syrian security forces.
The developments came shortly after President Bashar al-Assadof Syria denied that his forces had used poison gas against his own citizens, and as divisions between outside powers over how to handle the crisis showed no signs of easing.
In an interview with a Russian newspaper Izvestia, published on Monday, Mr. Assad said accusations that his forces had used chemical weapons were illogical and an "outrage against common sense." He warned the United States that military intervention in Syria would bring "failure just like in all the previous wars they waged, starting with Vietnam and up to the present day."
Mr. Assad's choice of a Russian newspaper to air his views seemed to reflect Moscow's strong support for the Syrian leader after last week's attack on the outskirts of Damascus, which claimed hundreds of lives.
On Sunday, a spokesman for Russia's Foreign Ministry, Aleksandr K. Lukashevich, said that those who advocated an armed response to any chemical weapons attack — without citing the United States or other countries — were prejudging the results of the United Nations inspections.
"In these conditions, we again resolutely call on all those who are trying to impose the results of the U.N. investigations and who say that armed actions against Syria is possible to show common sense and avoid tragic mistakes," Mr. Lukashevich said in a statement released on the ministry's Web site.
While Mr. Assad has said he would give weapons inspectors access to the site, the gesture has been greeted with widespread skepticism in the West, with critics saying that the offer came too late for inspectors to make an accurate assessment of what happened. The British foreign secretary, William Hague, complained on Monday that access was not "unimpeded" since it was limited to a "certain number of hours."
British officials also said on Monday that Prime Minister David Cameron would cut short a vacation in Cornwall, in southwest England, to return to London and head a meeting of senior ministers on Wednesday. His gesture seemed designed to heighten the mood of crisis as outside powers wrestle with Mr. Assad's refusal to bow to the West.
"If someone dreams about turning Syria into a puppet of the West, it simply will not happen," Mr. Assad told Izvestia. "We are an independent government, and we will battle with terrorism and we will freely build relations with those countries whom we want to."
In an interview Monday with Europe 1, a French radio station, Foreign Minister Laurent Fabius of France, said "all options" were still open in crafting an international response, but "the only option I do not envisage is to do nothing." France has been a close ally of the rebels seeking Mr. Assad's ouster in the country's civil war.
Mr. Fabius said there was no doubt that chemical weapons had been used and outside powers would negotiate a "proportionate response" in the "days to come."
In the welter of diplomatic maneuvering, Turkey, also a strong supporter of the rebels, said it would join an international coalition against Mr. Assad if the United Nations Security Council could not reach a consensus, Reuters reported, quoting Foreign Minister Ahmet Davutoglu in an interview with the Milliyet newspaper.
In London, Mr. Hague took a similar approach to an international response. "Is it possible to respond to chemical weapons without complete unity on the U.N. Security Council?" he told the BBC in a radio interview. "I would argue yes it is, otherwise it might be impossible to respond to such outrages, such crimes, and I don't think that's an acceptable situation."
On Monday, Russia's foriegn minister, Sergey V. Lavrov, stressed that even a Western strike on Syria would not prompt Russian military action. Asked a about the possibility at a news conference in Moscow, Mr. Lavrov was quoted by Reuters as saying, "We have no plans to go to war with anyone."
In the interview with Izvestia, Mr. Assad said, "America has taken part in many wars but could not once achieve its political goals for which the wars were started. Yes, it is true, the great powers can wage wars but can they win them?"
He said government troops would have risked killing their own forces if they had used chemical weapons. "This contradicts elementary logic," news reports quoted him as saying. It is "not us but our enemies who are using chemical weapons," he said, referring to antigovernment rebels as "the terrorists."
For his part, President Obama has not decided to take action, officials in Washington said on Sunday. But, moving a step closer to possible American military involvement in Syria, a senior Obama administration official said that there was "very little doubt" that Mr. Assad's military forces had used chemical weapons against civilians and that a Syrian promise to allow United Nations inspectors access to the site was "too late to be credible."
In Israel, a senior government official said Monday it was "crystal clear" that Mr. Assad's forces used chemical weapons last week and called the United Nations investigation effort a "joke." The official said that Iran, a close ally of the Syrian leader, should also be held responsible.
"The world cannot allow this to proceed," Yuval Steinitz, Israel's minister of international affairs, strategy and intelligence, told international reporters at a briefing Monday morning in Jerusalem. "The Iranians are already trying to isolate themselves from the use of chemical weapons. This is a kind of hypocrisy. You cannot be part of this terrible, brutal war and say, 'Yeah, I participate in the war but I isolate myself, I separate myself from the use of chemical weapons.' Assad today is almost a total proxy to Iran."
Echoing other Israeli leaders, Mr. Steinitz suggested that the Syria situation was a kind of harbinger regarding Iran's disputed nuclear program. "If Iran would get nuclear weapons, it's going to create a new, very dangerous new world, this is a global game-changer," he said.
Regarding the United Nations inspectors' search for evidence that chemical weapons were used, Mr. Steinitz said, "This is becoming a joke."
Noah Sneider contributed reporting from Moscow and Jodi Rudoren from Jerusalem.
