LUXEMBOURG (Reuters) - The European Union on Monday condemned Russia’s air campaign in Syria, saying it may be guilty of war crimes, and it vowed to impose more sanctions on President Bashar al-Assad’s government.

Russian President Vladimir Putin speaks during a news conference following the BRICS (Brazil, Russia, India, China and South Africa) Summit in the western state of Goa, India, October 16, 2016. Sputnik/Kremlin/Alexei Druzhinin via REUTERS

Calling for an immediate ceasefire in rebel-held east Aleppo, the European Union’s 28 foreign ministers sought to show their anger at the Russian-backed campaign, which has killed several hundred people including dozens of children since the collapse of a truce brokered by Russia and the United States.

“Since the beginning of the offensive by the regime and its allies, notably Russia, the intensity and scale of the aerial bombardment of eastern Aleppo is clearly disproportionate,” the EU said in a statement. Some 275,000 people are believed to be trapped in the area.

The bloc berated Moscow for “the deliberate targeting of hospitals, medical personnel, schools and essential infrastructure,” saying that targeting civilians with barrel bombs and chemical weapons “may amount to war crimes”.

The EU said the atrocities in Syria should be referred to the International Criminal Court, although it was unclear how or when.

It called for an immediate end to conflict, so a peace process could start after almost six years of war, seeking a wider role for EU foreign policy chief Federica Mogherini to talk to regional powers including Iran, Turkey and Saudi Arabia.

While the European Union has no military role in the conflict, the statement marked its harshest criticism of Russia’s role in Syria and came after days of negotiations and resistance from Russia’s allies in Europe.

It was Europe’s second attempt to isolate Russia diplomatically this month, after France and Spain led a push for a U.N.-backed ceasefire in New York, which Russia vetoed.

As food supplies run low in Aleppo, the scale of the destruction unleashed by the Syrian government’s Russian- and Iranian-backed offensive has horrified even Moscow’s long-time backers in Athens, Budapest and Nicosia, diplomats said.

Russia is Europe’s biggest energy supplier, and relations have sunk to lows not seen since the Cold War over the crisis in Ukraine. Some countries, including Austria and parts of the German government, worry about worsening ties even further.

But France and Britain pushed hard for the support of all the bloc’s 28 governments, hoping that a unified chastisement of Russia would help bring an end to the bombing since peace talks between Moscow and Washington broke down earlier this month.

France’s Foreign Minister Jean-Marc Ayrault said the European Union had a moral obligation to act and “to stop the massacre of the population of Aleppo.”

A briefing by U.N. Special Envoy Staffan de Mistura at the meeting in Luxembourg appeared to help swing doubters.

De Mistura, who has been at the heart of peace efforts in Geneva, warned that Aleppo was at risk of being reduced to rubble. “Between now and December, if we don’t find a solution for Aleppo, Aleppo won’t be there anymore,” De Mistura said.

SANCTIONS, BUT NOT ON RUSSIA

The European Union also said it was ready to put more Syrians under travel bans and asset freezes, suspecting them of directing attacks on civilians in Aleppo. That is in addition to the EU’s existing sanctions list and its oil and arms embargo.

The EU has a list of 208 people and 69 companies under sanctions, and that was likely to grow to pressure the Assad government and those benefiting from it, diplomats said.

In their statement, EU foreign ministers said the EU will act “swiftly ... with the aim of imposing further restrictive measures against Syria, targeting Syrian individuals and entities supporting the regime as long as the repression continues.”

Britain has also raised the prospect of sanctions on Russians involved in the Syrian conflict, diplomats told Reuters although that had less support on Monday.

British Foreign Secretary Boris Johnson, who held talks with U.S. Secretary of State John Kerry on Sunday in London, said London was considering imposing additional sanctions on Assad’s supporters, without naming Russia.

Spain would back Russian sanctions if they helped “bring Russia’s position closer to ours” acting Foreign Minister Jose Manuel Garcia-Margallo said.

European Union leaders will discuss Russia and possibly talk about new sanctions at a summit on Thursday. Russia’s closest EU allies - Greece, Cyprus and Hungary - oppose such penalties.

Austria, a transit point for flows for Russian gas to Europe, also voiced its opposition on Monday.

“The idea to have additional sanctions against Russia would be wrong,” Austria’s Foreign Minister Sebastian Kurz told reporters. “We do not need a further escalation,” he said.

German Foreign Minister Frank-Walter Steinmeier rejected imposing more punitive measures on Russia, although a German newspaper cited sources saying that Chancellor Angela Merkel favoured the idea.

The West imposed broad economic sanctions on Moscow over its 2014 annexation of Crimea and its support for rebels in Ukraine.