Pakistani security forces backed by helicopter gunships and artillery targeted militant hide-outs in the country's northwest on Friday, killing up to 30 rebels, a military statement said.

Two paramilitary troopers also died in the attack on Dara Adam Khel, a town in North West Frontier province, a day after a group of suspected militants hijacked four truckloads of supplies — including ammunition and other military materials.

Also on Friday, Pakistan's government responded angrily to a group of retired military commanders who appealed to President Pervez Musharraf to resign in order to promote democracy and combat religious militancy.

The timing of the call appeared designed to embarrass Musharraf, who was in Europe on a tour aimed at reassuring Western leaders about his ability to restore democracy and prevail in the escalating combat between government troops and Taliban rebels along Pakistan's mountainous border with Afghanistan.

Information Minister Nisar Memon described the retired military officials' call as unconstitutional, and said he was "dismayed at such lack of understanding of national issues by people who have held important positions in the past."

On Tuesday, Pakistan Ex-Servicemen's Society urged the U.S.-backed leader to resign immediately "in the supreme national interest," in a statement signed by more than 100 retired generals, admirals, air marshals, other senior officers and enlisted ranks.

Memon said that rather than issuing "irresponsible press statements," the group should focus on improving the welfare of retired military personnel.

On Friday, a former top intelligence official joined the calls for Musharraf to leave office, saying there was a "widespread belief in the country that you and your government has now become a huge part of the problem."

"While the army and paramilitary (forces) are deployed to fight in many parts of North West Frontier Province, the police and rangers are busy beating up civil society in the city streets," Masood Sharif, a former head of Pakistan's main domestic intelligence agency, said in a letter to the president.

While the group of retired servicemen does not speak for active officers, its tough stance could help erode military support for Musharraf, who was commander of the army until stepping down last month and whose popularity has waned considerably in the past year.

Speaking in Davos, Switzerland, where he was attending a meeting of the World Economic Forum, Musharraf described his critics as "insignificant personalities" whom he had dismissed from service.

He vowed that his government would carry on the fight against terrorism, and said parliamentary elections scheduled for Feb. 18 would be free and transparent.

This fall, Musharraf purged the Supreme Court — which was poised to scupper his recent re-election by a pliant parliament — and briefly suspended the constitution, setting back expectations of a restoration of democracy. The top court's chief justice remains under house arrest, along with other prominent judges and lawyers.

The political turmoil comes as Pakistan's army is increasingly engaged in combat with pro-Taliban militants in the tribal areas and other parts of North West Frontier Province.

In Washington, Defense Secretary Robert Gates said on Thursday that the United States was willing to send a small number of combat troops to Pakistan to help fight the insurgency there if Pakistani authorities asked for such help.

Gates said the Pakistani government has not requested any additional help in the weeks since al-Qaida and affiliated extremists have intensified their actions inside Pakistan. He stressed that the United States would respect the Pakistanis' judgment on the utility of American military assistance.

Also Friday, Pakistan successfully test-fired a medium-range, nuclear-capable ballistic missile, the military said, in one of the country's routine tests of the missiles in its arsenal.