"The red line is a common line for all of us: We are categorically against any use of weapons of mass destruction, be it chemical, be it biological, be it nuclear," Lavrov said. He added that the Syrian government has repeatedly assured Moscow that it is watching over those weapons and keeping the rebels away from the sensitive sites.
"Our partners agree with us that the biggest threat is the probability or possibility that the rebels get hold of those chemical weapons," Lavrov said.
In Damascus, another close Syrian ally, Iran, pledged continued support for Assad's regime. During a three-day visit to Syria, Tehran's top nuclear negotiator, Saeed Jalili, lashed out at countries supporting the opposition, saying they are "the enemies, claiming they are defending the Syrian people."
In the north, regime war planes hit rebel-held areas in Idlib province as troops fought rebels in Deir el-Zour in the east, an oil-rich area along Syria's border with Iraq, the Observatory said. Fighting also raged in the central provinces of Homs and Hama, in the restive suburbs of Damascus that were also hit by air strikes and in the southern province of Daraa, the birthplace of the uprising.
State-run SANA news agency said 15 people were killed and 22 others were wounded when a car, packed with explosives detonated prematurely in Idlib's Saraqeb city. The report said all the dead and wounded were "terrorists," a term the government uses for rebels.
Associated Press writers Geir Moulson and David Rising in Munich contributed to this report.
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.