German federal prosecutors accused Russia on Thursday, June 18, of ordering the killing of a former Chechen rebel in Berlin last summer and indicted a Russian man for the murder, which has severely strained diplomatic ties.

German investigators have gathered enough evidence to accuse the Russian man, identified only as Vadim K., of the murder as well as the illegal possession of a weapon, prosecutors said, Reuters reported.

"The accused accepted the order from state authorities to kill. He either hoped for a financial reward or shared the motive of the order-givers to kill a political opponent and thereby retaliate for participating in previous conflicts with Russia," they said in a statement.

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The dead man, identified in the statement as Tornike K., a Georgian citizen, was shot dead in a Berlin park last August as he was heading to a mosque. The killer had been on a bicycle.

Russia has denied any connection with the killing. President Vladimir Putin has said the dead man was himself a killer who had carried out bloody acts on Russian soil and that Moscow's requests for his extradition had not been heeded.

German Foreign Minister Heiko Maas welcomed the prosecutors' statement and called the killing an "extraordinarily serious" incident.

The Foreign Ministry summoned the Russian ambassador to make its position clear and Moscow understand that Berlin reserves the right to take further steps in this case, he added.

Germany expelled two members of the Russian embassy in December 2019 in connection with the case.

Berlin has also recently started taking steps against Moscow in connection with a hacking attack in the German parliament too, a spokesman said on Thursday.

Germany's foreign ministry last month called in the Russian ambassador to complain about the 2015 hack and said that possible sanctions were discussed against those responsible.

Russia has rejected allegations that its military intelligence was behind the cyber attack after media reported that data had been stolen, including emails from Chancellor Angela Merkel's constituency office.