Army helicopter gunships pounded militant positions in a tribal region in northwest Pakistan on Wednesday, killing an estimated 40 fighters, officials said.

Reports of the attack came hours after officials said militants had abducted 18 police officers from a checkpoint in the northwest, but the incidents did not appear to be related.

Militants in the region have stepped up attacks against security forces in recent months, adding to the pressures on President Gen. Pervez Musharraf as he seeks re-election.

Musharraf Slammed Over Ex-Prime Minister's Expulsion; Second Leader Barred From Entering Pakistani City.

They are already holding some 260 soldiers they kidnapped on Aug. 30 in the tribally governed South Waziristan area.

The gunship attack took place in North Waziristan, a rugged region on the border with Afghanistan that is home to scores of pro-Taliban fighters, spokesman Maj. Gen. Waheed Arshad said.

He said around 40 militants had been killed.

Hours earlier, suspected militants attacked a security checkpoint near Bannu, a town next to the restive region, abducting 18 police officers and wounding two others, officials said.

The insurgents fired rockets at the post before overrunning the position, said an intelligence agent who spoke on condition of anonymity due to the nature of his job.

Arshad said the militants abducted 18 police officers and left behind two others wounded in the attack. He gave no further details.

The United States has been pressing Pakistan to take a tougher action against insurgents amid concern that Taliban and Al Qaeda militants are gathering strength along the border with Afghanistan.