Nigel Gould-Davies, first secretary at the British Embassy in Moscow, was attacked by a group of unidentified teenagers on the night of May 26 while taking a nighttime stroll in the city of Chita, about 6,000 kilometers (3,700 miles) east of the Russian capital.
"The Prosecutor's Office of the Central district of Chita city has opened a criminal investigation in connection with the attack [on a British diplomat]," said Anatoly Uskov, a senior aide to the regional chief prosecutor.
The diplomat, who was on an unofficial trip to Chita on the invitation of the regional administration, was treated at a local hospital for minor facial injuries. He later filed a complaint with the local police.
"At this point, investigators have questioned several witnesses to the incident and reviewed a surveillance tape from a building on Theater Square [the site of the attack]," the official said, adding that the victim could not identify his assailants.
The incident comes at the time when Russian-U.K. relations could hit a new low following Britain's request to extradite Andrei Lugovoi in connection with the murder of ex-KGB officer Alexander Litvinenko in London last year.