The UN is to complain to the Syrian government and rebels after a convoy of chemical weapons inspectors came under sniper fire.
UN Secretary General Ban Ki Moon said he would ask the inspection team in Damascus to register “a strong complaint” so it never happened again.
The team is looking at five sites near Damascus where hundreds are reported to have been killed last week.
Russia has warned strongly against Western military action against Syria.
Russian Foreign Minister Sergei Lavrov said any intervention in Syria without a UN mandate would be a “grave violation of international law”.
The West, he told a news conference in Moscow, had not been able to come up with any proof of chemical weapons use while “saying at the same time that the red line has been crossed and there can be no delay”.
He was responding to suggestions from some Western countries that military action against Syria could be taken without a UN mandate over the suspected use of chemical weapons by government forces.