International peace envoy Lakhdar Brahimi says he remains worried about Syria's civil war after meeting President Bashar al-Assad in Damascus seeking a peaceful resolution to the conflict.

Brahimi said Monday he exchanged views with Mr. Assad on possible solutions, but the Algerian diplomat did not elaborate or describe any signs of progress. Syrian state news agency SANA quoted the president as saying he supports any peace effort that protects Syria's sovereignty and independence.

Brahimi arrived in Damascus Sunday, on his third visit since taking the post of U.N.-Arab League envoy in September. Since then, fighting between government and rebel forces has escalated nationwide, including around the Damascus airport. The lack of security at the facility forced Brahimi to travel to the Syrian capital by car from neighboring Lebanon.

Brahimi's arrival coincided with a large explosion that killed dozens of people in the central town of Halfaya in Hama province. The state news agency issued a report Monday denying opposition claims that government warplanes had bombed a bakery in the town, causing a massacre of civilians. Instead, SANA blamed the blast on armed terrorists, its term for rebels trying to end Mr. Assad's 12-year rule.

Videos of the Halfaya incident posted by activists on the Internet appeared to show that most of the dead were men. It was not clear if the bombed-out building seen in the images was a bakery. SANA accused “terrorists” of making films to falsely accuse the Syrian military of killing civilians.

Meanwhile, the Britain-based Syrian Observatory for Human Rights accused government forces of using a lethal gas to kill six rebels in the central city of Homs on Sunday. It said the rebels died after inhaling gas from government bombs that emitted white smoke, while survivors suffered headaches and seizures. The group called on the International Committee of the Red Cross to send a medical team to Homs to investigate.

Syria has repeatedly vowed not to deploy chemical weapons against its own people. Russian foreign minister Sergei Lavrov, whose government is a Syrian ally, said any use of such weapons by the Assad government would be “political suicide.” He made the comment in a Russian television interview broadcast Monday.

Rebels and exiled Syrian opposition groups have refused to negotiate with Mr. Assad, demanding instead that he step down and face justice. More than 40,000 people have been killed since the Syrian president began a violent crackdown on what began as a peaceful opposition uprising in March 2011.