ISLAMABAD — A suicide attack on the northwestern headquarters of Pakistan's spy agency Friday showed how militants have turned against an institution that once nurtured them and marked an escalation in their war against the U.S.-backed government.

The truck bombing was the second this year against offices of the intelligence agency, which has helped the CIA track down and arrest many al Qaeda suspects since 2001 but is still suspected by some Western officials of sympathizing with extremists, especially those fighting across the border in Afghanistan.

The early morning attack killed 10 people and devastated much of the complex in Peshawar city, which has been hit by many of the near-daily attacks in recent weeks by insurgents avenging an army offensive against their stronghold along the nearby frontier with Afghanistan. Another 55 people were wounded.

About an hour later, a second suicide car bomber attacked a police station farther south, killing six people, said police official Tahir Shah. Five of the dead were policemen in Bakkakhel village in Bannu district; the other was a civilian.

"This is a guerrilla war," said Mian Iftikhar Hussain, the information minister for North West Frontier Province, where Peshawar is the capital. "We will continue our action against these militant terrorists. That is the only way we can survive."

The attacks coincided with a visit to Pakistan by U.S. National Security Adviser Gen. James Jones. He met with military chief Gen. Ashfaq Parvez Kayani and Prime Minister Yusuf Gilani in the capital, Islamabad, about a three-hour drive south of Peshawar.

Pakistan's Inter-Services Intelligence agency was instrumental in helping to train jihadi groups to fight the Soviet Union in Afghanistan in the 1980s. Much of the activity took place in Peshawar, which lies at the entrance to the famed Khyber pass leading to Afghanistan.

It then trained and equipped thousands of young militants to use as proxies to fight its much larger neighbor India inside the disputed territory of Kashmir. The men were viewed as heroes by many in Pakistan. After the 2001 attacks in the United States, the agency largely severed its links with the groups.

Since then, the militants have formed alliances with al Qaeda and now present one of the deadliest threats to the country.

"There is no doubt that when we supported the war against the Russians, we trained and created this monster," said Dr. Riffat Hussain, a Professor of Defense Studies at Quaid-e-Azam University in Islamabad. "We never had the idea that this monster would turn against us."

The militants are waging a war against the Pakistani government because they deem it un-Islamic and oppose its alliance with the United States. The campaign of suicide attacks began in 2007, but the government appeared uncertain how to fight it, with many people believing that negotiations with the militants were possible.

A militant advance in April this year into the Swat Valley, which is in the northwest but outside the semiautonomous tribal areas where militants have traditionally been strong, appeared to push the country into taking firm action against the insurgency.

The army moved in force into the region and retook it from the Taliban, in a push that enjoyed popular support.

But the terror attacks on security, civilian, government and Western targets have only increased, with a surge starting in October when it became clear the army was poised to move into South Waziristan. More than 300 people have been killed, including 112 in a market bombing in Peshawar at the end of the month.

The government has vowed the attacks will not dent the country's resolve to pursue the operation in South Waziristan, where officials say the most deadly insurgent network in Pakistan is based. The army claims to be making good progress, though on Friday reported the loss of 12 soldiers over the last 24 hours, one of its largest single-day losses since the campaign began.

Militants have also targeted convoys in Pakistan delivering supplies to soldiers in Afghanistan.

Attackers fired rockets at a group of tankers near the southwestern city of Quetta on Friday that were delivering fuel to U.S. and NATO troops. One driver was killed and five tankers were torched, said local police chief Bedar Ali Magsi.

About 80 per cent of all nonessential supplies to Western forces in Afghanistan are trucked through Pakistan after landing at the Arabian Sea port of Karachi. NATO and U.S. officials say the attacks do not affect their operations.