BEIRUT - Syrian forces pounded the battered city of Homs with tank and mortar fire and troops pummelled several other rebel strongholds on Saturday, leaving at least 24 dead, opposition activists said.With the bloodshed showing no signs of abating, the UN-Arab League peace envoy for Syria, Kofi Annan, flew to Moscow, seeking Russian backing for his efforts to secure a ceasefire.Further to the north, security forces killed at least five people and wounded dozens more in raids on Saraqib, which lies in Idlib province bordering Turkey, activists said."There are dozens of tanks and armoured vehicles storming Saraqib now and there is heavy artillery fire," an activist called Manhal said via Skype.Mortars and heavy artillery fire also hit the city of Qusair, in Homs province, killing three civilians. There were reports of overnight clashes in the city of Douma, close to the capital Damascus.In the southern province of Deraa, birthplace of the revolt, the Syrian Observatory for Human Rights said a man was shot dead at a checkpoint in an area where a soldier had been gunned down. Three other soldiers were killed in an attack in the northeastern province of Hasaka, it said.Western and Arab states want Syrian President Bashar Assad to stand down but Russia, a long-time ally of Syria, has put the onus on the armed rebels and their foreign backers to make the first move.In a statement ahead of Sunday's meeting between Annan and Russian President Dmitry Medvedev, the Kremlin said it would be hard to enforce a halt to the violence "until external armed and political support of the opposition is terminated".More than a year after the start of the uprising against Assad, the prospect of a negotiated peace seemed more remote than ever, with clashes reported in numerous locations.At least 10 people were killed by explosions and sniper fire in Homs, the epicentre of the anti-Assad revolt, said activists who accused Syrian forces of shelling residential areas in the center of the city indiscriminately."The shelling started like it does every morning, for no reason. They are using mortar and tank fire on many neighborhoods of old Homs," an activist in Homs's Bab Sbaa district told Reuters via Skype.He said most residents in the area had fled to safer districts and many were trying to escape the city altogether.The Syrian government says rebels have killed about 3,000 members of the security forces and blames the violence on "terrorist" gangs. The official Sana news agency said the bodies of 18 "army martyrs", killed in various clashes, were buried on Saturday.