European Union leaders are holding a 2-day summit to discuss a variety of issues. Senior officials have criticized Russia over its bombings in Syria and have called on the EU to unite to urge Moscow to end its alleged attacks on civilians.

"That is why there has to be work on a truce and not just one of a few hours followed by several hours of bombing but a permanent truce. This is especially important to get humanitarian aid to people," Merkel said.

"All the options are open as long as the truce is not respected and as long as there is a will to crush a city, Aleppo. I go into this European Council to convince the Europeans that we should apply all the pressure required to prolong the truce," French president Francois Hollande said.

British Prime Minister Theresa May said that the EU must work together to put pressure on Russia. While European Council President Donald Tusk said he wants the bloc to keep all options open, including further sanctions if fighting continues. Leaders called for members to pursue medical evacuations in cooperation with the United Nations. They also want to push for a political transition in Syria by working with the region's main players.