Police in Moscow have opened a criminal investigation on suspicion of "hooliganism" after a top campaign aide for opposition politician and anticorruption activist Aleksei Navalny was attacked by an unknown assailant wielding a metal pipe.
A Moscow police spokesman told Interfax on September 16 that the case had been opened and police were looking for the perpetrator who attacked Nikolai Lyaskin the previous day. Lyaskin is the head of the Moscow office of Navalny's campaign for the 2018 presidential election.
Lyaskin suffered a concussion as a result of the attack and was treated at a hospital.
The incident was the latest in a string of assaults and other harassment of Navalny supporters around the country. Navalny himself suffered a chemical burn to his eye in April when an assailant splashed green antiseptic into his face.
Police closed the investigation into that incident in June without making an arrest.
Navalny is attempting to run in the election, but Russian officials have said he is ineligible because of a felony embezzlement conviction that he says was politically motivated.
Russian President Vladimir Putin has not announced whether he will participate in the election, but he is widely expected to seek and secure a fourth term as president.
The New York-based Human Rights Watch (HRW) said in a statement last week that "radical nationalists and pro-Putin groups have physically attacked and threatened" Navalny's campaigners, and that "official investigations into these incidents have not been effective."
HRW added that Russian police were "systematically" interfering with Navalny's attempts to run for president by raiding his campaign offices, "arbitrarily" detaining campaign volunteers, and carrying out "other actions that unjustifiably interfere with campaigning."
"The attack on Nikolai Lyaskin is, of course, the result of the lack of police action against the scum who carried out earlier attacks," Ivan Zhdanov, a lawyer for Navalny, wrote on Twitter.
Navalny posted a photograph of the alleged weapon on Twitter, writing: "What is this if not attempted murder?"