KIEV, Jan. 30 - President Petro Poroshenko cut short a visit to Germany on Monday after escalation of fighting in eastern Ukraine killed 12 and left a small town without electricity, water and heat supply in the middle of winter.

Heavy shelling from the territories controlled by pro-Russian separatists began on Sunday and continued through Monday, hitting the town of Avdiyivka near Donetsk, effectively breaking a ceasefire agreed last month.

The escalation comes a day after a phone conversation between U.S. President Donald Trump and his Russian counterpart Vladimir Putin.

“Seemingly, Putin perceived that he could launch an offensive after a phone call with Trump,” Anders Aslund, a senior fellow at the Atlantic Council and a former advisor to the Russian and Ukrainian government, tweeted on Monday.

“Can anybody in the White House explain why the Russian troops in Donbas started the offensive immediately after Putin’s call to Trump?” he said.

At least 12 people were killed, including three Ukrainian soldiers, in the latest violence, despite the fact of an "indefinite" cease-fire was agreed last month.

Ukraine’s Foreign Ministry called on the international community to put diplomatic pressure on Russia in order to stop the deadly escalation of the conflict.

“We demand that the Russian Federation stop immediately the fighting and stick to the cease-fire agreement,” the ministry said.

The ministry said targeting of non-military property of the Avdiyivka town by the pro-Russian militants is effectively a military crime that breaks the Geneva Convention of August 12, 1949.

“The power supplies cut completely to Avdiyivka and Yasynuvata, while 400,000 people were left w3ithout water and heat supplies,” the ministry said.

Poroshenko’s spokesman, Sviatoslav Tseholko, said the president has cut the visit to Germany due to the emergency unfolding in Avdiyivka and to make sure the government takes necessary steps to restore electric and heat supplies.

“The shelling from the militants led to the emergency situation that borders with the humanitarian catastrophe,” Tseholko said.

Poroshenko earlier met with German Chancellor Angela Merkel, and said the West should extend and strengthen sanctions against Russia if there is no progress in implementing the Minsk agreements on resolving the conflict.

Poroshenko also discussed the conflict in eastern Ukraine with German Foreign Minister Sigmar Gabriel

The conflict between Ukrainian government forces and the separatists has killed about 10,000 people in eastern Ukraine since April 2014. (nr/ez)