Iran, Russia could face EU sanctions for supporting Assad

European Union leaders are mulling sanctions against supporters of Syrian President Bashar al-Assad's regime if it fail to stop atrocities, according to a draft summit statement that appears to target Russia.

"The EU is considering all options, including further restrictive measures targeting individuals and entities supporting the regime, should the current atrocities continue," according to a draft obtained by AFP before the summit in Brussels that opens later on Thursday.

The draft broadens the language of EU foreign ministers on Monday who spoke only of targeting Syria and "Syrian individuals and entities supporting the regime".

Syria's external supporters are Iran and Russia, which backs Syrian government troops with warplanes that US and allied officials accuse of targeting civilians in airstrikes against towns and cities across the country.

Though Russia is not mentioned explicitly regarding sanctions, the draft statement sharpens the tone against Moscow and its role in the five-year civil war.

"The European Council strongly condemns the attacks by the Syrian regime and its allies, notably Russia, on civilians in Aleppo," according to the draft.

It asks them to urgently allow "unhindered humanitarian access to Aleppo" and to other parts of Syria while calling "for an immediate cessation of hostilities and for resumption of a credible political process under UN auspices."

Five years of efforts to put an end to the conflict in Syria have all failed, but over the past week world powers have made new efforts to broker a lasting truce.

The draft warns that "those responsible for breaches of international humanitarian law and human rights law must be held accountable."

The 28 leaders also ask EU foreign policy chief Federica Mogherini and the European Commission, the EU executive, to continue pursuing medical evacuations in cooperation with the United Nations.

The statement also asks Mogherini to push for a political transition in Syria by working with the region's main players which were not named.

On Thursday, Russian President Vladimir Putin said he was ready to prolong a unilateral ceasefire in Aleppo, after tough talks in Berlin where the leaders of Germany and France refused to rule out sanctions against Moscow.

"What is happening in Aleppo is a war crime, one of the first demands is that the bombardments by the regime and its (Russian) backers must end," French President Francois Hollande said after a meeting between the three leaders in Berlin.

German Chancellor Angela Merkel condemned the air raids on Syria's second city as "inhumane and cruel".

Aleppo, held by rebels determined to oust President Bashar al-Assad, has come under heavy bombardment since the Russian-backed military announced an offensive in late September to regain control of the east.

Airstrikes there have flattened numerous residential buildings and civilian facilities, in a campaign the European Union said could amount to war crimes.