ISLAMABAD (Reuters) - A bomb targeting Haqqani network militants in their hideout in Pakistan’s tribal areas bordering Afghanistan killed three people on Thursday, including two militants, a security official and a militant source said.

No group claimed responsibility for the blast.

The Haqqani network is known for bloody attacks against government institutions and foreign forces in Afghanistan, and its presence inside Pakistan is a major source of friction between Washington and Islamabad.

The United States and Afghanistan accuse Pakistan of providing a safe haven to senior Haqqani commanders and allege the group operates freely on Pakistan’s side of the porous frontier, charges that Pakistan has repeatedly denied.

“It was the office of our commander Naik Muhammad,” a Haqqani network source told Reuters about the attack near the Pakistan-Afghanistan border in Pakistan’s South Waziristan region.

“At the present we can not say who is behind this blast. It damaged our office,” he said.

When asked what he meant by term “office”, the source said it was a meeting place for Haqqani and other militants.

One of those wounded was regional Haqqani commander Jamshed Khan, he added.

A Pakistani security official in the region said three people were killed in the attack, including two Haqqani militants, and 11 were wounded.

U.S. officials have urged Pakistan to act against Haqqani militants but scant progress has been made. Privately, Pakistani officials say they fear such a move could see Haqqani militants turn their guns on Pakistani targets.

Since coming to office, U.S. President Donald Trump has taken a hardline stance on Pakistan, recently saying during an interview with Fox News that the South Asian country doesn’t “do a damn thing” for the U.S. despite receiving billions of dollars in aid.

Trump’s comments have further frayed the already fragile relationship between the two countries. Pakistani Prime Minister Imran Khan hit back at Trump by saying the United States is turning Pakistan into a “scapegoat” to mask its own failures in Afghanistan.