A memorial in central Moscow to the murdered Russian opposition leader Boris Nemtsov has been vandalised.
Slogans and insults were scrawled on photographs of the politician and a street sign saying “Nemtsov Bridge” was defaced.
An obscure nationalist group, which is sympathetic to pro-Russian rebels in Ukraine, said it was responsible.
Mr Nemtsov was shot on 27 February while walking with his girlfriend on the bridge, near the Kremlin.
Russian President Vladimir Putin has condemned the murder and vowed to find the killers.
Pictures emerged on social media, apparently taken by the vandals themselves, showing people desecrating tributes marking the spot where Mr Nemtsov was attacked.
A pro-Kremlin organisation called South-East Ukrainian Civil Movement (SERB) later claimed responsibility, saying its actions were a response to calls to rename Moscow’s Bolshoy Moskvoretskiy bridge in Mr Nemtsov’s honour, according to Russian news website Lenta.ru.
Allies of Mr Nemtsov, a former deputy prime minister and veteran liberal politician, condemned the damage.
“Some cowardly scumbags have trashed Nemtsov’s memorial,” Ilya Yashin, co-founder of his political party, wrote on Twitter.
Mr Nemtsov’s supporters have said the killing was linked to his criticism of the Kremlin.
He was killed days before a march he had been organising against the conflict in Ukraine.
Mr Yashin told the BBC earlier this month that a report Mr Nemtsov had been compiling on Russia’s role in the crisis would be released in April.
Officials have not revealed a motive for the murder.
Several men from the Caucasus region have been arrested for the murder, prompting suggestions of an Islamist link to the attack. One of those charged has said he was forced into a confession.
Ukraine’s military has been battling pro-Russian separatist rebels in the country’s east since April 2014.
The Ukrainian government, Western leaders and Nato say there is clear evidence that Russia is helping the rebels with heavy weapons and soldiers.
Independent experts echo that accusation. Moscow denies it, insisting that any Russians serving with the rebels are “volunteers”.