LAGOS, Nigeria — A “witch hunt” for gay people has led to arrests in at least four of Nigeria’s 36 states, Amnesty International said Wednesday, blaming a new law criminalizing gay organizations and meetings as well as same-sex marriage.

It said the law’s disregard for human rights mirrors that of the military dictators who ruled Africa’s most populous nation until 1999.

Nigerian human rights defenders say they fear further persecution of gay people under the law in a notoriously corrupt country where police are known to make arrests to extort money and blackmail victims.

“With the stroke of a pen, President (Goodluck) Jonathan has essentially turned Nigeria into one of the world’s least tolerant societies,” London-based Amnesty International said in a statement calling for the law to be withdrawn without delay.

The Associated Press reported Tuesday that 38 people had been arrested in the northern state of Bauchi since Christmas, and some have been charged in court with belonging to a gay organization.

Amnesty said 10 people have been detained since Monday in four southern states.

It said police in Bauchi have confirmed they have a list of suspects of minority sexual orientation who are under surveillance that also is being used to “find out who their victims are.”