WASHINGTON • United States Secretary of State John Kerry has called for a war crimes investigation of the bombing campaign by Russia and the Assad government in the Syrian civil war, charging that they were continuing to attack hospitals as part of a deliberate strategy to terrorise civilians, the New York Times reported yesterday.

Mr Kerry's appeal comes as Syrian rebels yesterday lost ground on two fronts to government forces and the Islamic State in Iraq and Syria (ISIS) group, British-based monitoring group the Syrian Observatory for Human Rights reported.

While the government forces recaptured territory in several western areas, ISIS reclaimed several villages in their counter attack near the Turkish border, Reuters reported yesterday, citing the Observatory.

"Russia and the regime owe the world more than an explanation about why they keep hitting hospitals, and medical facilities, and children and women," Mr Kerry said on Friday, before meeting with his French counterpart at the State Department.

"These are acts that beg for an appropriate investigation of war crimes, and those who commit these would and should be held accountable for these actions," Mr Kerry added. "This is a targeted strategy to terrorise civilians."

Mr Kerry's remarks came one day before the United Nations Security Council was expected to vote on a French-drafted resolution that calls for a ceasefire in Aleppo and the grounding of Russian and Syrian warplanes that have been pummelling the besieged city.

Russia has asserted that it is targeting terrorist groups, and Mos- cow's envoy to the UN, Mr Vitaly Churkin, threatened to veto the measure, the New York Times reported. "I cannot possibly see how we can let this resolution pass," he said on Friday.

Still, the US and its Western partners appear to be hoping they can put pressure on Russia and the Syrian government to ease their offensive by highlighting attacks on civilians.

Russian fighter jets have been bombing eastern Aleppo for the past two weeks, joined by their allies in the Syrian Air Force. Russia says the targets are the Nusra Front, a banned terrorist organisation.

The UN envoy, Mr Staffan de Mistura, this week offered to personally escort Nusra fighters out of the city, saying pointedly that their presence was being used as an "alibi" to destroy the city; for that to happen, Russian and Syrian air strikes would have to stop.

At least 376 civilians have been killed by Russian and Syrian strikes in eastern Aleppo since Sept 23, Mr de Mistura said.

It is not clear how Mr Kerry thinks a war crimes investigation might be carried out in the face of Russian opposition, according to the New York Times.