Russia -- one of the most tenacious allies of the Syrian regime -- has called on the the government of President Bashar al-Assad to allow a mission of United Nations inspectors to investigate alleged chemical attacks in the suburbs of Damascus and guarantee safe passage for U.N. workers entering the country, according to Reuters.
Russia has also called on forces opposed to Assad's government to guarantee the investigators' safety. Russia's appeal to Syria comes after months of warnings from Moscow against foreign intervention in the two-year civil war that has left more than 100,000 people dead and displaced nearly 2 million Syrians, including 1 million children.
Video footage that has not been independently verified by Al Jazeera shows what appears to be the remnants of a chemical weapons attack.
U.N. Secretary-General Ban Ki-moon asked the Syrian government to allow U.N. inspectors to investigate the allegations "without delay."
Ban said the use of chemical weapons in Syria would constitute a "crime against humanity" and a violation of international law. He also warned Assad's government of "serious consequences" if their use is proved.
Opposition groups alleged Assad's government on Wednesday fired rockets with chemical warheads into the Damascus suburbs of Arbeen, Zamalka and Ein Tarma. The attacks reportedly left hundreds dead.
"This is a grave challenge to the entire international community -- and to our common humanity, especially considering it occurred when the United Nations expert mission is in the country," Ban said.
Ban on Thursday instructed Angela Kane, the U.N.'s high representative on disarmament affairs, to travel to Damascus, according to a statement.
Meanwhile, activists said government warplanes on Thursday again hit areas where the alleged chemical attack took place.
Syria's government, which has repeatedly denied the use of chemical weapons, offered no public response to the U.N. calls for its team to inspect the site of the attack.
Earlier Thursday, France said the international community would need to respond forcefully if allegations proved true that the Syrian government was responsible for chemical attacks on civilians.
Foreign Minister Laurent Fabius told French television network BFM that a decision would be made "in other ways" if the U.N. Security Council couldn't arrive at one, but he didn't specify the alternatives.
"He appears to be hinting at threatening some kind of military action in order to put pressure on Syria," said Al Jazeera's Jacky Rowland, reporting from France.
The Syrian National Coalition said more than 1,300 people died in the alleged attack, and videos and photographs showed scenes of dozens of people foaming at the mouth and of bodies stacked up in morgues.
Foreign governments demanded immediate access to the sites of the alleged attacks for the U.N. chemical-weapons investigation team.
On Thursday, Turkish Foreign Minister Ahmet Davutoglu said a "red line was crossed" in Syria and called for international action.
Washington previously described chemical weapons use as a red line that might prompt it to intervene militarily in Syria.
President Barack Obama said Friday in a CNN interview that chemical weapons use in Syria is "a big event of grave concern" and that the U.S. has a more abbreviated time frame for dealing with Egypt and Syria.
Obama didn't specificy what the U.S. response may be.
"We don't expect cooperation [from Syria], given their past history," Obama told CNN's Chris Cuomo. "As difficult as the problem is, this is something that is going to require America's attention and hopefully the entire international community's attention."
Al Jazeera and wire services