The opposition, divided between Islamists and liberals, is holding a "National Salvation Congress" to try to unite behind the goal of ending 41 years of Assad family rule, but is struggling to agree on whether to form a shadow government.

"I'm for anything that unifies the Syrian people and helps our people inside, and unifies our ranks in confronting this illegitimate repressive regime that has usurped power and human rights," opposition figure Wael Al-Hafez told the meeting in Istanbul, echoing comments made by others. "We want to raise the intensity of the peaceful confrontation by civil disobedience and to choke the regime economically and paralyze the state with the least damage."

The West has criticized Assad's crackdown on four months of protests demanding political freedoms. On Friday, his troops killed at least 32 civilians, including 23 in the capital Damascus.

Secret police killed one protester and wounded five on Saturday when they opened fire at pro-democracy demonstrators in the eastern border town of Albu Kamal.

The opposition said security forces had targeted a wedding hall in Damascus where it had planned to hold a simultaneous conference, connected by video link to the one in Istanbul.

"Several martyrs are fallen and others have been arrested," said Haitham Al-Maleh, a former judge who was among political prisoners released by Assad in March when the uprising began.

"The regime cannot deny us our freedoms. This state is for the Syrians, not Assad family's property," Al-Maleh told the meeting in Istanbul of several hundred people.

Most of his audience have lived in exile for years, if not decades, and many have paid a heavy price for their dissent in previous crackdowns by the ruling Baath Party. Unlike other meetings in recent months in Turkey, some members of the opposition inside Syria managed to attend.

The dissidents at the meeting appeared to fall into two camps — Islamist and secular liberals. Splits seemed to open among them over whether to form a government-in-waiting or wait to see how the uprising unfolds, and they could opt to form a united body without presuming a leadership role.