VIENNA (Reuters) - Russia must investigate reports by human rights groups that dozens of men are being held and tortured in Chechnya because they are believed to be gay, the rights arm of the Organization for Security and Cooperation in Europe (OSCE) said on Friday.

The allegations that up to 100 men are being detained prompted a protest outside the Russian embassy in London on Wednesday. Russian independent newspaper Novaya Gazeta has reported that at least three of those men have been killed in secret prisons described as “concentration camps”.

“The authorities in the Russian Federation must urgently investigate the horrific reports of human rights violations against allegedly gay men in Chechnya, as well as identify, prosecute and punish any known perpetrators,” the head of the OSCE’s Office for Democratic Institutions and Human Rights (ODIHR), Michael Link, said in a statement.

The OSCE, once a rare forum for discussion between East and West during the Cold War, has 57 participating states stretching from North America to Russia and Central Asia. ODIHR deals with election monitoring and human rights in those states.

A spokesman for Ramzan Kadyrov, president of the southern Russian region of Chechnya and a vocal supporter of Russian President Vladimir Putin, was quoted by Russia’s Interfax news agency as denying the alleged abuses have taken place.

“Nobody can detain or harass anyone who is simply not present in the republic,” Alvi Karimov was quoted as telling Interfax.

Link said Moscow had to step in.

“Given the reported unwillingness of local authorities to investigate and prosecute the serious violations alleged to have been committed by security services, it is incumbent upon Russian Federation authorities to intervene and protect all those remaining at risk,” he said.

The Kremlin could not immediately be reached for comment on the OSCE’s call for an investigation. Previously, Kremlin spokesman Dmitry Peskov has said he was aware of the reports about abuses against gay people in Chechnya but that it was up to Russian law enforcement agencies to investigate, and therefore not an issue on the Kremlin’s agenda.

ODIHR is a widely respected institution but the OSCE’s ability to act is constrained by the fact that it tends to reach decisions by consensus, effectively granting all participating states a veto.

An ODIHR spokesman was not immediately available for comment on what further steps the organization might take.