The Russian human rights group Memorial has named 13 detainees among 27 feared to have been secretly shot dead by police in Chechnya.
The group said it pressed Chechen officials for information on the missing men, but "they refused to tell us whether they were dead or alive".
Memorial spoke to family and friends of the 13, after Novaya Gazeta had spoken of 27 shot dead one night in January.
A Chechen minister condemned the Novaya Gazeta report as a "lie".
Information Minister Jambulat Umarov said it was the "sick fantasy" of a journalist who "is trying to revive the gay topic".
The alleged victims of summary execution were not among the dozens of gay men reportedly persecuted in Chechnya, whose fate triggered an international outcry earlier this year.
There were reports of torture and gay activists helped some victims to flee the Muslim-majority North Caucasus republic.
History of abuses
Novaya Gazeta specialises in exposing human rights abuses and corruption in Russia. It has long documented abuses in Chechnya, whose authoritarian leader Ramzan Kadyrov is close to President Vladimir Putin.
On 9 July, Novaya Gazeta named 27 male Chechen detainees believed to have been shot on the night of 25-26 January, then secretly buried.
The information came from two senior officials - in Chechnya's Investigative Committee and presidential administration - the paper said. Despite that, Novaya Gazeta said it could not confirm the deaths because there was official silence.
The paper named the 27, but said there were believed to be other victims too, all of whom had disappeared in a police crackdown in December.
That crackdown - described by Novaya Gazeta as "mass arrests" - followed an assault on 17 December in which a gang killed a policeman and stole his car. After a chase they were killed by security forces.
Human rights groups have accused Mr Kadyrov's feared "Kadyrovtsy" paramilitary police of arbitrary arrests and torture. Thousands of Chechens died or disappeared during two Russian wars against Chechen separatist rebels.
Reports 'look credible'
An Amnesty International expert on Chechnya, Denis Krivosheev, told the BBC that the allegations by Memorial and Novaya Gazeta "look very credible".
"We've worked with them for years, they are extremely cautious and often they have separate sources," he said. The reports are "entirely consistent with what we know about the authorities' impunity in Chechnya, a pattern of human rights abuses there", he explained.
"It is unimaginable that abuse on this scale could take place without the full knowledge of Kadyrov and his associates," he said.
Mr Krivosheev voiced concern that Russia was only at the "pre-investigation" stage regarding the plight of gay Chechen men.
"In the last couple of years we've seen a deterioration of human rights in Chechnya, with attacks on human rights defenders and a policy of targeting the families of people suspected of links to insurgents.
"Fear permeates Chechen society, so people are unwilling to provide evidence," Mr Krivosheev added.