Russia and China are joining international calls for an investigation into an alleged poison gas attack in a suburb of Syria's capital, as U.S. President Barack Obama said the reported incident is of "grave concern."
Russia's foreign ministry Friday said claims by Syria's opposition that hundreds died in a poisonous gas attack this week should undergo an objective investigation and it called on Syria to cooperate.
Moscow also called on rebel forces to guarantee safe passage for United Nations investigators who are already in the country looking into previous allegations of chemical use. The ministry released the statement following a call between Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry.
China's foreign ministry Friday also backed calls for a U.N. investigation, with a spokesman telling the state-run Xinhua news agency that China "resolutely opposes" the use of chemical weapons no matter which side is responsible.
The United States has been pushing for a U.N.-led investigation. Mr. Obama told CNN that officials are still gathering information but called the reported attack a matter of "grave concern."
Mr. Obama also acknowledged many people around the world are looking to the U.S. to take action. But he said, "the notion that the U.S. can somehow solve what is a sectarian, complex problem inside of Syria sometimes is overstated."
Syrian opposition leaders and activists have released video of scores of adults and children lying dead on the ground without signs of injury. Neither the number of people killed nor the cause of death could be independently confirmed.
The Syrian government denies the allegations.
On Friday, British Foreign Secretary William Hague called a chemical weapon attack "the only possible explanation" and placed the blame on the government of Syrian President Bashar al-Assad.
"I know some people in the world would like to say that this is some kind of conspiracy brought about by the opposition in Syria, I think the chances of that are vanishingly small. And so we do believe this is a chemical attack by the Assad regime on a large scale, but we would like the United Nations to be able to assess that, so for those who don't believe that, for those who doubt that, the evidence can be gathered, but that is certainly our opinion."
The former top U.S. weapons investigator for Iraq, Charles Duelfer, also says it appears the videos are genuine.
"This is quite powerful and it's clearly something that hasn't been faked. I mean, these are real people. You couldn't create this, much to the - I know there are some international parties that say, well, this could be something created, a 'provocation', in the words of the Russian foreign minister. That's not a convincing position."
Duelfer says, as a result, the U.N. personnel already in Syria and awaiting access to the site will be under enormous pressure.
"In essence they've got their finger on the trigger of the international community where military force can be unleashed."
The United Nations has formally asked Syria to let U.N. personnel "swiftly investigate" the scene. U.N. Secretary-General Ban Ki-moon has said that any use of chemical weapons in Syria would amount to a "crime against humanity" that would result in "serious consequences."
Mr. Assad's government has consistently denied using chemical weapons. It has accused the opposition of using chemical weapons earlier this year near Aleppo. The U.N. team already on the ground in Syria was sent to investigate those claims.