ISLAMABAD, Oct 1, 2009 (AFP) - Pakistan may be buoyed by a push against the Taliban in Swat, but analysts warn the Islamist threat cannot be quashed without a determined assault against militants entrenched in the tribal belt.

Three suicide car bombings that left 28 people dead in the northwest in the past week show a new Taliban leadership willing and able to inflict carnage, while key militant chiefs remain at large despite multiple offensives.

"The Taliban remain a dangerous force, capable of causing a great deal of damage," a recent editorial in English-language paper The News said.

"The war begun against them must continue. There can be no let up... there will have to be a campaign in Waziristan," it added, referring to the wild semi-autonomous region where Islamist rebels hold sway.

For years Pakistan's military has oscillated between launching offensives against Islamist insurgents and signing peace deals with the rebel leadership holed up in the lawless tribal belt that borders Afghanistan.

But the march of militants across the one-time tourist playground of Swat and neighbouring districts, advancing to within 100 kilometres (60 miles) of Islamabad in April this year, sparked a fierce air and ground onslaught.

With more than 2,140 militants reported killed, the government in early July said the verdant valley was almost cleared of the Taliban threat.

Next in the military's sights was the tribal region of Khyber, the fabled land route into Afghanistan and the main supply line for the more than 100,000 US and NATO troops fighting in Pakistan's war-stricken neighbour.

Helicopter gunships and paramilitaries thrust into Khyber on September 1, targeting Lashkar-e-Islam (Army of Islam), a homegrown militia led by former bus driver Mangal Bagh, which has loose links to the Taliban.

Military spokesman Major General Athar Abbas said the operation was essential as militants fleeing other offensives in Swat and nearby districts "were coming and taking refuge in this agency."

Analysts and local residents, however, question how successful the Khyber operation has been when no high-profile targets have been captured or killed. "Everybody knows where Mangal Bagh is living - why don't they go after him and target him?" Khyber resident Jamil Afridi told AFP.

Now the army claims to be mopping up there and looming on the horizon is the prize of North and South Waziristan - the main bastions of the Taliban leadership, and also a hideout and training ground for Al-Qaeda fighters.