Clashes between Ukrainian government troops and pro-Russian separatists intensified in Donetsk on Thursday, with battles breaking out near the city’s main train station and airport.

French freelance photographer Antoine E.R. Delaunay posted a photo to Twitter showing heavy smoke between the train station and airport in Donetsk, a city of 900,000 in eastern Ukraine where rebels have regrouped after government troops took the upper hand after three months of fighting with the separatists.




Delaunay also said he heard “sporadic gunshots” around the airport in Donetsk.

Ukraine’s military said it had a “nasty surprise” in store for pro-Russian separatists hunkering down in Donetsk after they were flushed out of their stronghold in Slaviansk, about 70 miles north, over the weekend, Reuters reported.

Three Ukrainian soldiers were killed in attacks Wednesday night in the eastern portion of the country, where the separatists are concentrated. Reuters reported the military sustained further casualties on Thursday but did not have an exact figure. About 200 government troops have been killed since April. Hundreds of civilians and rebels have also died in the conflict.

Calls are growing for a cease-fire. New Ukrainian President Petro Poroshenko called a cease-fire late last month that quickly broke down. But the leaders of France and Germany want Russian President Vladimir Putin to use his influence to “exert all necessary pressure on the separatists and bring them to negotiate effectively.”

French President François Hollande and German Chancellor Angela Merkel also called on Putin to better monitor the border between Ukraine and Russia, where fighters are easily transporting equipment and weapons to the rebels.