Syrian forces killed at least 32 civilians on Friday, including 23 in the capital Damascus, in an intensifying crackdown on protests against President Bashar al-Assad, activists said.It was the highest death toll in the central neighbourhoods of Damascus since the uprising erupted four months ago in the southern Hauran Plain near Syria's border with Jordan.

"Tens of thousands of Damascenes took to the streets in the main districts for the first time today, that is why the regime resorted to more killings," said one activist by telephone from Damascus. He declined to be named for fear of being arrested.

The killings prompted the opposition to cancel their planned National Salvation conference in Qaboun neighbourhood of Damascus on Saturday after security forces killed 14 protesters outside a wedding hall where the conference had been due to take place, opposition leader Walid al-Bunni told Reuters.

"Secret police also threatened the owner of the wedding hall. We decided to cancel the meeting to save lives," Bunni said by telephone from Damascus.

Bunni said prominent opposition figures and activists would still hold a separate conference in Istanbul on Saturday.

The rest of those killed in Damasacus were in Barzeh, where one protester had died, and in Rukn al-Din quarter of the city, where security forces fired protesters killing eight people.

Two protesters were killed in the southern suburb of Qadam, said the Local Coordination Committees.

Assad, facing the greatest challenge to 40 years of Baath Party rule, has sought to crush demonstrations that broke out in March. But although rights groups say some 1,400 civilians have been killed, the protests have grown.

"These are the biggest demonstrations so far. It is a clear challenge to the authorities, especially when we see all these numbers coming out from Damascus for the first time," said Rami Abdelrahman, head of the Syrian Observatory for Human Rights.

Activists and witnesses said police fired live ammunition and teargas in the capital Damascus and suburbs. They killed four in the southern city of Deraa, the cradle of the uprising.

Three protesters were shot dead in the northwestern province of Idlib, near the Turkish border, where troops and tanks have attacked villages, the witnesses and activists said. Two people were also killed in the city of Homs.

A witness in the Rukn al-Din district of Damascus said hundreds of young men wearing white masks resisted security forces with sticks and stones.

"Down, down Bashar al-Assad", they chanted.

In the city of Hama, scene of a 1982 massacre by the military, live video footage filmed by residents showed a huge crowd in the main Orontos Square shouting "the people want the overthrow of the regime".

At least 350,000 people demonstrated in the eastern province of Deir al Zor, the Syrian Observatory for Human Rights said. Syrian forces shot dead two pro-democracy protesters there on Thursday, residents said.

Reuters