Hundreds of thousands of Syrians staged the largest protests since the revolt began in mid-March [Getty images]

Syrian troops backed by tanks have stormed the town of Zabadani and rounded up more than 500 people, including Ali Abdullah, a leading opposition figure, amid reports of more deaths in the central city of Homs, activists say.

A Syria-based human-rights activist, Mustafa Osso, said government forces early on Sunday entered Zabadani, near the border with Lebanon and about 40km northwest of Damascus.

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Osso said authorities have detained more than 500 people since Friday, when hundreds of thousands of Syrians turned out for the largest protests since the revolt began in mid-March.

The Local Co-ordinating Committees, which help organise and track the protests, confirmed the Zabadani raid and said about 2,000 military and security forces swarmed in after cutting the town's telephone services, internet connections and electricity.

Also on Sunday, another rights activists said at least 30 people had been killed in Homs the last 24 hours in clashes between supporters and opponents of Bashar al-Assad.

"More than 30 civilians have been killed over the past 24 hours in Homs in clashes that broke out late on Saturday between the opposition and supporters of the regime," said Rami Abdel Rahman of the London-based Syrian Observatory for Human Rights. 

Turkey conference

The developments come a day after exiled Syrian dissidents met in Turkey to urge their countrymen to launch a campaign of civil disobedience to try to force Assad from power.

Syria's political opposition elected part of a standing committee to push for Assad's removal, but failed to create a shadow government at Saturday's conference.

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The gathering of some 350 mainly expatriate Syrians, called the National Salvation Congress, elected a 25-member board late on Saturday in Istanbul.

A final statement said activists in Damascus would elect another 50 board members, and that each would then elect smaller executive committees of 11 and 13 members respectively.

Divisions among a liberals, Islamists, Arabs and Kurds ruled out any immediate progress in forming a shadow government, reports from the conference said.

The aim was to hold simultaneous meetings in the Syrian capital and Istanbul. Sima Abadraboh, a political activist and organiser of the Istanbul event, said the Syrian military encircled the location in Damascus on Friday and broke up preparations for the meeting.

Despite the crackdown, some Syrian opposition activists met at a small private location in Damascus on Saturday and used an internet phone link to address the Istanbul gathering.

Source: Agencies