ISLAMABAD, (Reuters) – Pakistani warplanes struck a stronghold of Pakistani Taliban leader Baitullah Mehsud on Saturday in retaliation for the killing of an anti-Taliban cleric the previous day, the military said.

U.S. officials, thankful their nuclear-armed ally has gone on the offensive to stop a Taliban tide sweeping the northwest, said Pakistan looked set to mount a significant offensive against Mehsud’s forces in South Waziristan bordering Afghanistan.

Mehsud’s network is blamed for many suicide attacks including the assassination of Zardari’s wife, former prime minister Benazir Bhutto, in December 2007.

Hours before the attack on Mehsud’s stronghold, President Asif Ali Zardari vowed in a televised address to wage war against militancy “to the end”.

Under pressure in their sanctuaries, Islamist militants have responded with a wave of bomb attacks in Pakistani cities, including one on Tuesday that killed nine people and devastated the top hotel in Peshawar, the main city in the northwest.

A prominent anti-Taliban cleric who had condemned suicide bombings was killed in a suicide bomb attack in the city of Lahore on Friday. Six other people were killed.

“In response to the suicide attack … two terrorist compounds were targeted,” the military said in a statement, adding the number of casualties could not be ascertained.

Intelligence officials in the area, who declined to be identified, said seven militants were killed and five wounded.

Rising violence has fed fears for Pakistan’s stability and for the safety of its nuclear arsenal, but the military action has reassured the U.S., which needs its Muslim ally’s help to defeat Al Qaeda and stabilise neighbouring Afghanistan.

On Thursday, the U.S. House of Representatives approved tripling aid to Pakistan to about $1.5 billion a year for five years to help combat extremism through development. Pakistan is now the biggest recipient of U.S. aid.

In the past few days the Pakistan has launched strikes on Taliban across the northwest, most notably in Bannu district at the gateway to Waziristan, where according to the military more than 130 militants have been killed since Tuesday.

The military says about 1,300 militants have been killed in Swat and adjoining areas since the army swung into action in late April. The military said on Saturday 41 “terrorists” and one soldier had been killed in the previous 24 hours.

Independent casualty estimates were unavailable.

The airstrike on Mehsud’s compounds in Makeen village came amid expectations of an imminent offensive in South Waziristan, as the army enters the final stages of a campaign to rid the Swat valley, northwest of the capital, of Taliban.

Artillery also pounded militant positions in Mehsud territory overnight, intelligence officials in the area said and a U.S. official said the Pentagon anticipated combat operations against the Mehsud network.

The Pakistani military began combat operations in Waziristan in early 2004, but struck controversial peace deals with militants after each short-lived campaign.

The military has launched attacks in other parts of the northwest over the past few days in what analysts see as an attempt to keep the militants distracted and to “soften up” their positions.

Interior Minister Rehman Malik told Reuters on Friday the military wanted to stop militants regrouping outside Swat.

On Saturday, warplanes bombed militant hideouts in the Mohmand region, killing at least seven people, a paramilitary spokesman said.

In Bajaur, at the northeasterly end of the ethnic Pashtun tribal belt, air strikes and artillery shelling killed nine militants, intelligence officials said.

On Saturday, militants attacked a police bus in Kohat, killing a policeman and a passer-by and wounding nine police.