Suspected U.S. missiles killed four people in northwest Pakistan on Friday, the latest in a surge of such attacks since a suicide bomber staged a deadly assault on CIA employees just across the frontier in Afghanistan.

The attack was the sixth in just over a week in North Waziristan, an unusually intense bombardment that also follows repeated calls by the United States for Pakistan to do more against militants there blamed for attacks on American and NATO forces in Afghanistan.

The area is the stronghold of the Haqqani network, an Afghan Taliban group with links to Al Qaeda. Its militants are responsible for cross-border attacks and could have played a role in the Dec. 30 attack that killed seven CIA employees in Khost province, analysts believe.

The U.S. does not comment on the strikes or their targets. It has carried out more than 50 of them since last year, most by unmanned plans believed operated by the CIA with the cooperation of Pakistani intelligence. They have been more common since the Obama administration took over.

Two Pakistani intelligence officials said a pair of missiles Friday evening hit a house and a vehicle in a village near Miran Shah in North Waziristan. They said four people were killed and three injured, but did not identify them. The officials spoke on condition of anonymity because they were not authorized to release the information to media.

The attacks since last week have killed 31 people, many of them militants, according to Pakistani officials interviewed after the strikes. The area is impossible to visit without the consent of the militants, making independent reporting impossible.

Pakistan's government publicly condemns the drone strikes as violations of its sovereignty, though it is thought that have a secret deal with Washington allowing them. One attack in August killed Baitullah Mehsud, the leader of the Pakistani Taliban, which have been leading a deadly insurgency against the Pakistani government from their sanctuary in the border region.

Pakistan's army has fought the militants in parts of the region over the last year, but it has not taken action against the Haqqani network yet. Critics say this is because it wants to use the group as a future asset to influence Afghanistan and stay ahead of its regional rival, India, after the Americans withdraw. The Pakistan army say it lacks the resources to tackle all the militant groups in the area and must pick its enemies.

Growing violence in Pakistan has not been confined to the country's volatile northwest.

Earlier Friday, eight suspected militants were killed when the explosives they were handling went off prematurely in a house in the southern city of Karachi, authorities said. Officers seized 25 hand grenades, three automatic rifles, and two suicide jackets, police chief Waseem Ahmad said.

Ahmad said there were "indications" the men intended to stage a commando-style raid on a court where Interior Minister Rehman Malik was appearing on corruption charges, but presented no evidence to back up the claim. Charges against Malik were recently reopened following the striking down of an amnesty protecting him and thousands of other officials from past criminal allegations.

"These men wanted to create a hostage situation and present their demands. Packed tin food with them showed that they planned to spend several hours at such a place," he said.

Two hours after the blast minister Malik attended the court hearing, which had been scheduled since last month.

Malik's lawyer said he appeared in court to ask the judge that he not have to appear in person at future trials for security reasons. Like other top officials, Malik strictly controls information about his movements for fear it could be used by militants plotting to kill him.

The reopening of the corruption case against Malik in December has weakened him politically and critics have called on him to step down. Not having to appear in court would lessen the political impact of the case, at least in the short term. He has denied any wrongdoing in the case, which centers on his alleged role in a 1996 scam involving the sale of bitumen.