Thousands of people have been killed in Syria by the earthquake that struck its border region with Turkey on February 6 but aid has been slow to reach the most affected areas.

Syrian government forces and allied militias have raped and sexually assaulted women, girls and men in a campaign to punish opposition communities - acts that constitute war crimes and crimes against humanity, UN investigators say.

US Secretary of State John Kerry is in Moscow for talks to try to bridge gaps with Russia over the political process to end Syria's civil war.

The US is intensifying diplomatic efforts to end the "hell" of Syria's civil war even as it increases support for moderate rebels, US Secretary of State John Kerry has said.

The United States announces that Iran may take part in talks to end the civil war in Syria and warned of increased military action against the Islamic State.

US Secretary of State John Kerry expresses concern to Moscow over reports of Russian military build-up in Syria, the state department says.

At least 16 people, including 13 children, are killed when Syrian air force jets bombed a town in Deraa province on Tuesday, activists say.