* Clearance to visit Moscow sought
* Kremlin assurances said worthless without full probe
* Other killings in Russia cited
By Robert Evans
GENEVA, July 21 Seven U.N. human rights experts asked Russia on Tuesday to allow them into the country to help investigate last week's murder of leading rights activist Natalia Estemirova.
The move by the seven -- from both developed and developing countries -- followed a call by U.N. High Commissioner for Human Rights Navi Pillay for a thorough and independent probe into the killing, which sparked worldwide condemnation.
Estemirova was abducted in her native Chechnya and her body was found in the neighbouring republic of Ingushetia.
The experts said they recognised the Russian authorities had condemned the murder and pledged that every effort would be taken to catch and punish the killers of Estemirova, who represented Moscow rights body Memorial in Chechnya.
"However, these assurances will be worth little unless the authorities take steps that go beyond what has been done in the past which has all too often led to a cycle of impunity," they said in a statement issued through the Untied Nations in Geneva.
"We offer our assistance to the Russian authorities in light of the failure to effectively and impartially investigate the killings and attacks on a number of human rights defenders in recent years ... and to bring the perpetrators to justice."
The experts were referring, among other cases, to the still unsolved killings, in Moscow, of journalist and rights activist Anna Politkovskaya in 2006 and of a prominent rights lawyer and a reporter early this year.
The seven, special rapporteurs to the U.N. Human Rights Council, included extrajudicial execution sleuth Philip Alston of Australia, violence against women specialist Yakin Erturk of Turkey, and Manfred Nowak of Austria, who reports on torture.
Their intervention was seen as aimed at getting round the blockage on quick investigations on such issues in the Council, where Russia lines up with a majority group of Islamic and African states that resists action affecting any of them.
Earlier this month, six of the seven -- who report to the 47-member Council -- criticised Iran over its handling of protests following June's contested elections and called for "independent international scrutiny" there.
Their latest move came as Chechen leader Ramzan Kadyrov, accused by rights groups and domestic critics of killing opponents and suppressing free speech, launched a lawsuit against Memorial for linking him to Estemirova's death.
Rights groups also say Kadyrov, a former fighter against Russian control of Chechnya who switched sides and rose to power with Moscow's support, was behind the killing of Politkovskaya, a friend of Estemirova.
But Russia's President Dmitry Medvedev, who said last week he was determined to find and punish Estemirova's killers, has rejected such charges, dubbing them "primitive" and aimed against the government.
A spokesman for Kadyrov has also denied his involvement, saying that as the dead woman defended human rights "she could not possibly have had enemies among clear-thinking people".
The other four experts calling on Moscow to allow a visit were Guatemalan Frank La Rue who reports on freedom of speech, Margaret Sekaggya who investigates violence against human rights defenders, Argentine Leandro Despouy, expert on independence of judges, and Santiago Corcuera Cabezut of Mexico who chairs a U.N. group on forced disappearances. (Editing by Alison Williams)