AT least 28 civilians were killed in Syria overnight, including 16 in the capital Damascus and a child, as security forces opened fire to quell the largest anti-regime rallies in four months, activists said.

US Secretary of State Hillary Clinton said Syria cannot now return to the way it was before anti-regime protests erupted on March 15.

Rights activist Abdel Karim Rihawi said the deaths also included two in Kadam and four in Douma, both suburbs of the capital, in addition to three in the northwestern city of Idlib and two more in the southern town of Daraa.

Neighbourhoods in Damascus bore the brunt of the violence, with 12 killed in Qabun, three in Rukn Eddin and another in Barzeh, said Mr Rihawi, who heads the Syrian League for the Defence of Human Rights.

The capital’s suburbs also saw the death of a child killed in Jobar, four adults in Douma and one in Kadam. Three people were killed in the northern city of Idlib and two others in the southern town of Daraa, Mr Rihawi added.

More than one million Syrians turned out in just two cities — Hama and Deir Ezzor — to protest against the regime of President Bashar al-Assad and demand the release of hundreds of detainees seized in earlier pro-democracy rallies.

“More than a million people demonstrated today in Hama and Deir Ezzor,” another activist, Abdel Rahman, said. “It’s a major development and a message to the authorities that protests are getting bigger.”

In the central city of Homs, 15 people were wounded when security forces opened fire, pro-democracy militants said of some of the mass demonstrations staged after Friday prayers.

Mr Rihawi added that 15 protesters were wounded in Kiswe, in Damascus province.

Security agents used live ammunition to disperse protesters in the Qabun and Barzeh areas of Damascus, while more demonstrators infiltrated the Madaya, Harasta and Saqba regions, Mr Rihawi said.

The official SANA news agency said “armed men fired on security forces and citizens in the areas of Qabun and Rukn Eddin in Damascus”.

Syrians had been urged to demonstrate to demand the release of people imprisoned in the bloody crackdown on democracy protests.

State television reported “the death of a civilian killed by armed men at Idlib”, and added: “The military and security services are protecting demonstrators against armed men in Daraa province.”

Activists issued an appeal for nationwide protests to mark a day of “Freedom for the Hostages” on The Syrian Revolution 2011 Facebook page, a driving force behind the demonstrations.

Like their cousins across the Arab world, Syrians have adopted Fridays, when they gather for the main weekly Muslim prayers, as their main outlet for dissent.

In tandem with the latest protests, organisers called for a simultaneous “Conference of National Salvation” to be held tonight (AEST) in Damascus and Istanbul to look at ways to oust Assad.

A statement said the conference will “draw up a road map that will bring the country out of despotism towards democracy and define the mechanism to overthrow the regime (as) sought by the (people of the) Syrian street”.

Mrs Clinton told reporters in Istanbul that “Syria can’t go back to the way it was before”, and that it was clear that the Assad regime was making empty promises that were not moving the country forward.

“I don’t think we know how the opposition in Syria will be able to conduct itself, what kind of avenues for action are open to it,” she said.

“What we are seeing from the Assad regime, the barrage of words, false promises and accusations is not being translated into a path forward for the Syrian people, and it is ultimately the responsibility of the Syrian people to choose and chart their own course,” she said.

Mrs Clinton also said Mr Assad “has lost his legitimacy in the eyes of his own people because of the brutality of their crackdown, including today”.

Since the protests began, violence has killed 1419 civilians and 352 members of the security forces, while more than 1300 people have been arrested, the Syrian Observatory for Human Rights said on Thursday.

State television, meanwhile, said gunmen in the western flashpoint city of Hama, where about half a million people have protested on the past two Fridays, had kidnapped two members of the security forces and a student.