Islamabad: The brother of senior Afghan Taliban commander Siraj Haqqani has been killed in a US missile strike in northwestern Pakistan, Pakistani intelligence officials said Friday.

The death was the latest in a string of blows to militants operating in Pakistan and neighboring Afghanistan, including the capture in recent weeks of the Taliban's No. 2 leader, that together are seen as the most significant strike against the insurgents in years.

Mohammed Haqqani and three other close associates of Siraj Haqqani were killed when missiles struck a house on Thursday night in the Dande Darpa Khel area of North Waziristan, near the border with Afghanistan, two Pakistani intelligence officials said.

The officials spoke on condition of anonymity because they were not authorized to speak publicly to the media.

The officials said the attack was apparently aimed at Siraj Haqqani, a top Taliban commander with suspected close ties to Al Qaida who is accused of masterminding ambushes of American troops in Afghanistan. It was not known if Siraj Haqqani was hurt in the strike.

The Haqqani network is an autonomous militant group that nonetheless has ties to al-Qaida and technically pledges allegiance to Afghan Taliban chief Mullah Omar. The group also has a history of links to Pakistani intelligence that some suspect continue today.

The US considers the network one of the biggest threats to its operations in Afghanistan, and has pressed Pakistan to move against the Haqqanis in their sanctuary in North Waziristan, a tribal region bordering Afghanistan. Pakistan has held off on any major operation, but may be aiding the U.S. missile campaign.

The network's leader, Jalaluddin Haqqani, was a respected commander and key U.S. and Pakistani ally in resisting the Soviet Union after its 1979 invasion of Afghanistan. In the 1980s and 1990s, Haqqani also hosted Saudi fighters including Osama bin Laden. That hospitality is believed to still extend to al-Qaida and other foreign fighters on both sides of the border.

Jalaluddin Haqqani, believed to be in his 60s or older, is said to be too ill to do much now, and his son Siraj is running the network. The group is alleged to make its money through kidnappings, extortion and other crime in at least three eastern Afghan provinces.

President Barack Obama has stepped up the use of missile strikes from unmanned drones in Pakistan's lawless tribal area since taking office, partly in response to the Pakistani government's reluctance to target Taliban militants who are not deemed a direct threat to the state.

The arrest earlier this month of Mullah Abdul Ghani Baradar, second only to the Taliban's leader, Mullah Mohammad Omar, and of Taliban "shadow governors" for two Afghan provinces have raised hopes that Pakistan's powerful intelligence services have changed strategy and are more willing to go after senior militants.

The crackdown also comes as U.S., NATO and Afghan troops fight a major offensive against militants in the Taliban stronghold of Marjah in southern Afghanistan.