Pakistani authorities say students at a radical mosque in the capital, Islamabad, have abducted four policemen.
A cleric at the mosque Abdul Rashid Ghazi said Friday the abductions were in retaliation for the detention of at least nine students by intelligence agents in the past two weeks.
Police confirmed the abductions at the mosque and said that negotiations for their release were under way.
In other violence Friday, militants in the North Waziristan tribal region killed an Afghan man whom they accused of spying for the United States.
Authorities said the body was found near the Afghan border and that there was a note attached saying he was a spy.
Militants in Pakistan's remote regions have killed many locals for allegedly spying for the United States or backing the Pakistani government's campaign against Taleban and foreign fighters.