Police are hunting down and torturing homosexuals in Nigeria, rights groups say, only days after President Goodluck Jonathan signed new anti-gay measures into law.
Campaigners also allege that gay men were tortured into naming dozens of others, to be arrested.
Homosexual acts were already illegal in Nigeria, but the Same Sex Marriage Prohibition Act - passed with a conspicuous lack of announcement or fanfare on Monday - means anyone belonging to a gay organisation can get up to 10 years in jail, and anyone married to someone of the same sex can get up to 14 years.
The law was met with condemnation from the United States, Britain and Canada, with US Secretary of State John Kerry saying it "dangerously restricts freedom" of expression and association of all Nigerians.
And UN human rights chief Navi Pillay said: "Rarely have I seen a piece of legislation that in so few paragraphs directly violates so many basic, universal human rights."
According to the Associated Press news agency, accounts varied of how many arrests were made in Nigeria's Bauchi state on Tuesday, and a local law enforcement official denied that anyone was tortured.
Dorothy Aken'Ova, executive director of Nigeria's International Centre for Reproductive Health and Sexual Rights, said an undercover officer joined a group being counseled on AIDS, pretending to be gay.
Aken'Ova, whose organisation is helping provide legal services to the men, said police then detained four gay men over the Christmas holidays and tortured them until they named others allegedly belonging to a gay organisation. She gave no details on what she called torture. She said police have now arrested 38 men and are looking for 168 others.
Chairman Mustapha Baba Ilela of Bauchi state Shariah Commission, which oversees regulation of Islamic law, said that 11 gay men have been arrested over the past two weeks. He said community members helped "fish out" the suspects and that "we are on the hunt for others."
He said all 11 arrested signed confessions that they belonged to a gay organisation, but that some of them retracted the statements in court. He denied any force was involved, saying: "They have never been tortured, they have never been beaten, they have never been intimidated."
Shawn Gaylord of Human Rights First, a Washington-based organisation, said he was alarmed by the reports of torture and arrests.
"When discriminatory bills like this are passed, we are always concerned that they set the stage for violence and ill-treatment in society even when they are not enforced," Gaylord said in a statement. "But the fact that this law is being enforced so quickly and forcefully demonstrates the full extent of Nigeria's human rights crisis."
Jonathan has not publicly expressed his views on homosexuality, but his spokesman, Reuben Abati, told the AP on Monday night: "This is a law that is in line with the people's cultural and religious inclination. So it is a law that is a reflection of the beliefs and orientation of Nigerian people. ... Nigerians are pleased with it."