German Chancellor Angela Merkel ’s government expelled two Russian embassy staff in response to what it says is a lack of cooperation by Moscow in the investigation of a contract killing of a Georgian man in a Berlin city park.

The German foreign ministry’s decision came after Germany’s federal prosecutor said earlier on Wednesday that there are sufficient indications that the ethnic Chechen victim was killed either on the order of an agency of the Russian federation or of the Chechen republic. “We haven’t seen that Russia has offered support in the investigation of this murder,” Merkel told reporters after a Nato summit in England. The German leader said she discussed the matter with allies at the meeting.

The case could complicate Merkel’s delicate relationship with Russian President Vladimir Putin. She said she’ll discuss the matter with Putin in Paris on December 9, when they’ll meet to seek a path to peace in easter n Ukraine .

Those efforts may now be overshadowed by the fresh tensions. “We consider the statements from the Germans about the expulsion of two employees of the Russian embassy in Berlin to be groundless and unfriendly,” the Russian foreign ministry said, according to RIA Novosti . “We won’t accept a politicised approach to the investigation. We are forced to carry out retaliatory measures.”

The hit-job in Berlin took place in broad daylight on August 23. The victim is thought to have fought against the Russian army in Chechnya. The suspected gunman, a Russian citizen, was apprehended soon after but refused to talk to investigators. Germany’s federal prosecutor says he was taken off a Russian wanted list in 2014 for murder and later reappeared with a new passport. They also said he was employed by a company with links to the Russian defence ministry.

