Annan in Moscow mission as Syrian fighting rages.

The UN-Arab League envoy to Syria, Kofi Annan, has arrived in Moscow amid reports of 24 new civilian deaths in Syria.

Mr Annan will try to persuade Russia to take a firmer stance against the Syrian government.

Next week, he will travel to China which, like Russia, has generally supported Syria at the UN.

Ten of the new deaths were reported in Homs, the city at the heart of the revolt against Bashar al-Assad.

"The shelling started like it does every morning, for no reason," an activist in the city's Bab Sbaa district told Reuters news agency via Skype.

"They are using mortar and tank fire on many neighbourhoods of old Homs."

The activist added that most residents in the area had fled to safer districts and many were trying to escape the city altogether.

Foreign media face severe restrictions on reporting in Syria, and it is hard to verify the claims of either side.

The Associated Press news agency has seen video apparently showing a huge explosion in Homs.

The footage, released by an activist group called the Shaam News Network, shows a large ball of fire and plume of black smoke.

According to the London-based Observatory for Human Rights, a total of 24 civilians died on Saturday as well as 15 soldiers and two rebels.

One activist, Nureddin al-Abdo, told AFP news agency that government troops backed by 26 tanks had attacked the town of Saraqeb in the north-western province of Idlib.

All the signs are that the regime intends to continue its drive unless armed rebels simply surrender, the BBC's Jim Muir reports from Beirut in neighbouring Lebanon.

That is the message to Kofi Annan as he urges the government to call an immediate halt to the use of heavy arms in populated areas, our correspondent says.

Whether the route ahead lies with his peace efforts, or with further confrontation, the opposition clearly needs to unify its divided ranks, he adds.

It has announced moves to unite its fragmented military efforts and also to hold a meeting in Istanbul on Monday, to try to bring the various political groups together behind a shared vision for Syria's future.