German-Russian relations have been plunged into crisis after German federal prosecutors said there were “sufficient indications” that the Russian state was behind the murder of a Chechen rebel in a Berlin park in August.

The case will refocus attention on the campaign of assassination that the Kremlin has unleashed on its political opponents abroad. The killing of Zelimkhan Khangoshvili occurred just 18 months after the Russian double agent Sergei Skripal and his daughter Yulia were poisoned by a nerve agent in Salisbury, England.

Germany’s foreign ministry said on Wednesday it had expelled two Russian diplomats over Moscow’s failure to help investigate the Khangoshvili murder, in a sign of the damage the case has inflicted on relations between the two countries.