MOSCOW -- Colleagues, friends, and relatives of Boris Nemtsov have honored the slain Russian opposition politician on what would be his 58th birthday, vowing to continue pressing for justice.
Activists of the opposition groups Solidarnost and Parnas visited Nemtsov's grave at a Moscow cemetery on October 9 and then joined a larger crowd on the bridge near the Kremlin where he was shot dead at close range on February 27, 2015.
Parnas co-Chairman Mikhail Kasyanov, who was President Vladimir Putin's first prime minister but later joined Nemtsov in opposing the Kremlin, expressed hope that international institutions will be involved in investigations of his killing.
But he said that in the current circumstances, with severe tensions straining Russia's relationship with the West, cooperation between Russian law enforcement and international investigators was impossible.
A Moscow court convicted five men from Russia's North Caucasus region of Chechnya guilty of Nemtsov's murder and sentenced them to prison in July, but relatives and associates believe his killing was ordered at a higher level.
The Russian authorities "have not even searched for the organizers of the crime and those who ordered it," Nemtsov's daughter, Zhanna Nemtsova, told RFE/RL in an interview in Berlin, where a two-day forum on Nemtsov is being held on October 9-10.
Nemtsova said that "the murder will never be forgotten and we will constantly be raising the issue until it is fully investigated."
She also said it was wrong for the Russian authorities to classify the crime as the murder of a private individual, contending that her father was a public figure who was assassinated.
Nemtsova said that the Parliamentary Assembly of the Council of Europe (PACE) will hold hearings on her father's killing on October 11.
In Moscow, dozens of activists the gathered at a makeshift memorial on the bridge where Nemtsov was shot.
Nemtsov, a former deputy prime minister and regional governor and a longtime critic of Putin, was a lawmaker in the Yaroslavl Oblast and co-chairman of Parnas at the time of his killing.
His slaying drew international condemnation and underscored the dangers faced by Russians who oppose the Kremlin.
As with previous killings -- including the fatal shooting of investigative journalist Anna Politkovskaya in 2006 -- government critics have voiced suspicion that the culprits will never face justice because an honest investigation could lead to figures who are close to Moscow-backed Chechen leader Ramzan Kadyrov or to Putin and his inner circle.
Nemtsov's birthday comes two days after thousands of Russians protested against the government on Putin's 65th birthday, at demonstrations called for by jailed opposition politician and Putin critic Aleksei Navalny. Navalny and Nemtsov were among the leaders of large antigovernment protests in 2011-12.