Pakistani troops Thursday mounted helicopter and mortar attacks on militants in the lawless northwest, where officials said 23 insurgents and three civilians have been killed.

The violence in North Waziristan tribal district came a day after a suicide bombing at a military checkpoint killed five soldiers and wounded 34 others.

Ansarul Mujahideen, a little-known militant group linked to the Tehreek-e-Taliban Pakistan (TTP), claimed responsibility for Wednesday's suicide attack.

A senior military official said 23 militants were killed overnight in fighting with security forces in North Waziristan, a known hotbed of the TTP and Al-Qaeda linked militants.

Clashes erupted after the insurgents attacked a convoy of security forces which was returning after rescuing soldiers wounded in Wednesday's bombing, the official said on condition of anonymity.

The death toll could not be verified independently because of an ongoing search operation and curfew in the area. The area is also off-limits to foreign journalists and aid groups.

Helicopters attacked compounds in the morning while troops fired mortars at intervals throughout the day at suspected militant hideouts.

A senior security official said the cordon and search operation was still going on in the town of Mirali and surrounding areas.

Local resident Mohabbat Khan told AFP the security forces also demolished a few compounds in Mirali where they suspected the presence of rebels.

He added that the landline telephone service had been suspended in the area.

Earlier, local security officials said six of the suspected militants had been killed during raids on two hotels.

"Pakistani security forces raided two hotels in the area close to the site of the suicide bombing and intense gunbattles left six suspected militants dead and 12 others wounded," a local security official told AFP.

Separately, shells fired by Pakistani security forces hit a house in Moski village and killed a woman and her two daughters, the local official said.

Military officials did not confirm the civilian deaths.

The TTP has led a bloody campaign against the Pakistani state in recent years, carrying out hundreds of attacks on security forces and government targets, mainly in the northwest.