Syria: At least 28 civilians killed as security forces open fire

At least 28 civilians were killed in Syria overnight as security forces opened fire on the largest anti-regime protests in four months, activists say.

Neighborhoods in the nation's capital of Damascus bore the brunt of the violence, with 16 dead, including a child, Australia's ABC website reports.

Activists called for nationwide protests to mark a day of "Freedom for the Hostages" on The Syrian Revolution 2011 Facebook page.

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, AFP reports.

The large turnout is "a major development and a message to the authorities that protests are getting bigger," according Abdel Rahman, the head of the Syrian League for the Defense of Human Rights.

Security agents used live ammunition to disperse protesters in some suburbs of Damascus.

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

Relations between Syria and Washington are under further strain after the U.S. embassy and the ambassador's residence was attacked.

The French embassy was also attacked.

Clinton said the attacks would not deflect the world's attention from the "real story" in Syria, ABC reports.

"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."

Mr Assad "has lost his legitimacy in the eyes of his own people because of the brutality of their crackdown, including today," AFP reports.

The attack came three days after the French and American ambassadors visited the besieged city of Hama to support pro-democracy protests.

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

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 Deraa province."

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.

Since the protests began, the violence has killed 1,419 civilians and 352 members of the security forces, while more than 1,300 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, AFP reports.