DHAKA, Bangladesh (AP) — Authorities in Bangladesh have arrested a rights activist with ties to the country’s main opposition party, apparently over allegations the group he works for made against government forces after a deadly crackdown on a protest in May.

Detectives picked up Adilur Rahman Khan from his residence in the capital late Saturday, said Dhaka Metropolitan Police spokesman Masudur Rahman. Khan is secretary of the Dhaka-based rights group Odhikar.

Home Minister Mohiuddin Khan Alamgir said Sunday that Khan was arrested on “specific charges,” but did not elaborate.

Odhikar’s director, A.S.M. Nasiruddin Elan, said the group did not know what the charges were. He said Khan was ordered to be detained for five days while he’s interrogated.

Elan said police wanted to question Khan for allegedly violating the country’s information technology act in connection with a crackdown on a hard-line Islamic group.

Khan’s arrest is apparently connected to a May crackdown by security officials on a rally in Dhaka by the Islamic organization Hefazat-e-Islam, which says it is a non-political group formed to fight those who want to undermine Islam in Muslim-majority Bangladesh.

Opposition parties said the government used excessive force and killed scores of people during the early morning action.

Odhikar said 61 people died in the crackdown. The government asked the rights group to hand over its report about the killings so it could investigate, but Odhikar refused, citing security concerns for the victims’ families.

The government has said it found no evidence of mass killings during the crackdown.

Khan is known to be close to the main opposition Bangladesh Nationalist Party, headed by former Prime Minister Khaleda Zia. He was appointed as a state lawyer with the Attorney General’s office during Zia’s last term as prime minister, which ran from 2001 to 2006.