PESHAWAR, Pakistan – Suicide attackers struck a police headquarters and a military convoy on Sunday in Pakistan’s northwest, killing as many as 38 people in an intensifying anti-government campaign in an area long known as a haven for the Taliban and al-Qaida.

Militants in the Afghan border region disavowed a 10-month old truce with the government that critics said gave them a safe haven from which to launch attacks on Afghan, U.S. and NATO forces in Afghanistan.

The government has deployed thousands of troops to the region to thwart calls by extremists for a holy war to revenge the bloody storming of Islamabad’s Red Mosque last week, and the region’s Islamic militants are increasingly training their attacks on the soldiers — and apparently other government targets as well.

In Dera Ismail Khan, near South Waziristan, the bomber at the police headquarters struck as recruits were testing to join the force, said Gul Afzal Afridi, a police officer.

“It was a suicide bombing and the attacker mingled among the scores of people gathered for the test and physical examination,” Afridi said.

More than 150 people were on the grounds when the bomber struck. The blast killed 20 people and wounded 35, said police officer Mohammed Aslam. He said the head of the suicide bomber and his suicide vest had been found.

Elsewhere, in a mountainous area of North West Frontier Province near the Afghan border, a convoy of army and paramilitary troops was attacked by suspected militants, Maj. Gen. Waheed Arshad said. An official who spoke on condition of anonymity because he was not authorized to speak with the press said 18 people were killed and 47 wounded; Arshad said 11 soldiers and three civilians had died.

“These were two suicide attacks in which two blue Suzuki vans were used as well as an (improvised explosive device) blast,” said Arshad, who said 39 soldiers were wounded by the explosions.

On Saturday, a suicide bombing killed at least 24 soldiers and wounded 29 on a road near Daznaray, a village about 30 miles north of Miran Shah, the main town in the North Waziristan tribal region, Arshad said.

In Washington, Sen. John Warner, R-Va., a senior member of the Senate Armed Services Committee, said the U.S. was concerned about the developments in Pakistan.

“Pakistan is faced with a very fragile political situation. Musharraf is up for reelection, and we all hope he will be reelected,” he told “This Week” on ABC.

The document disavowing the 10-month old truce between militants and the government was distributed in the bazaar of Miran Shah, complained that government forces had attacked militants, failed to pay compensation created problems at check points.

“The peace agreement has ended,” said a militant spokesman, Abdullah Farhad, confirming the document’s authenticity.

Signed by the shura, or council, of North Waziristan, the document warned local militia and elders against cooperating with the government. The signatories referred to themselves as the Taliban, a term commonly used by some Pakistani militants in northwest Pakistan.

On Saturday, at least 24 soldiers were killed and 29 wounded on a road near Daznaray, about 30 miles north of Miran Shah, Arshad said.

The driver plowed his explosives-laden vehicle into the convoy in one of the most lethal suicide attacks in recent months. Although no one claimed responsibility, Arshad said he could not rule out the possibility that it was a reaction to the assault on the Red Mosque.

Tensions are high in Pakistan after the raid, which ended an eight-day siege with a hard-line cleric and his militant supporters, who had sought to impose a Taliban-style Islamic rule in Islamabad. More than 100 died during the standoff.

The region along Pakistan’s border with Afghanistan has seen increased activity by local militants, the Taliban, and — according to a recent U.S. assessment — al-Qaida.

Arshad said reinforcements had been sent to the northwest to beef up some 90,000 troops already in the region. Officials say the fresh troops have moved into at least five areas.

In Islamabad, authorities Sunday detained Shah Abdul Aziz, a National Assembly member from an alliance of religious parties, for allegedly inciting people against the government during the Red Mosque siege.

He would be detained for 30 days, said Chaudhri Moohammed Ali, a senior Islamabad district official.

Aziz, who told a local television station that he had done nothing wrong, was among a delegation of ministers and religious scholars who attempted without success to peacefully resolve the standoff.