Islamabad, Pakistan (CNN) -- Suicide attackers killed at least 41 people and wounded more than 61 on Saturday at a camp for displaced people in northwestern Pakistan, officials said.
A spokesman for Lashkar-e-Jhangvi Al almi told CNN the militant group takes responsibility for the attacks and that they were in retaliation for two recent Sunni conversions.
The spokesman, Umar, told CNN that two months ago two Shia women from Kachai village in Kohat district converted from Shia to Sunni, and were killed by Shia Muslims in their village. The camp targeted in Saturday's bombings were filled primarily with Shia.
The attacks occurred about noon in Kohat, a town in the North West Frontier Province, said Khalid Khan Umarzai, a local commissioner.
There were two blasts from two separate suicide attackers at the camp, which is for people who have fled the military offensive in the area, officials said. Police said both suicide bombers were wearing burqas.
When people came to help those injured in the first blast, a second one went off, wounding and killing more people.
Pakistan military has stepped up its offensive against the Taliban in recent weeks, causing a flood of displaced people to pour into camps.
The U.N. Office for the Coordination of Humanitarian Affairs issued a statement deploring the strike, saying it occurred when people were lined up at a humanitarian assistance registration center.
"These were people who had fled their homes," said Martin Mogwanja, humanitarian coordinator. "They had suffered displacement, they'd suffered losing their homes. They'd come to the registration point considering it a safe haven. They'd come for help. They'd come for sanctuary. We mourn their loss, and condemn their killing."
More than 250,000 people are registered as internally displaced people in the towns of Kohat and Hangu after fleeing the fighting between government troops and the Taliban in Orakzai and Kurram, two districts in the country's tribal region.
The United Nations had been providing food and shelter to these people, but such services were temporarily suspended as officials reviewed the security situation.
Journalist Nazar Ul-Islam contributed to this report.