ISLAMABAD: Pakistan claimed Tuesday to have killed 42 Taliban in some of the heaviest fighting of a major offensive after the second gun attack on a senior army officer in the capital in less than a week.

Warplanes and helicopters waged multiple bombing sorties for an 11th day against Tehreek-e-Taliban Pakistan (TTP) in South Waziristan, pressing its most ambitious battle yet in a tribal area infested with Al-Qaeda-linked rebels.

It has been impossible to obtain independent information from the battle field, which is sealed off to journalists and aid workers, and from which more than 200,000 civilians have fled -- a third of the estimated district population.

Pakistan has won US endorsement for its vow to crush TTP, which has claimed some of the worst bombings in a two-year campaign that has killed more than 2,280 people in the nuclear-armed country on the border with Afghanistan.

Jet fighters and helicopter gunships pounded Ladha and Makin in South Waziristan on Tuesday, where ground troops hope to encircle militant bastions after claiming to have captured strategic mountain tops and villages.

The military, which is so far the only source of casualty figures, said 42 militants and one soldier were killed, bringing to 239 the total number of insurgents and to 31 the number of troops to have died during the operation.

Security forces surround Nawazkot, one of the Taliban's strongholds, and militants were killed in fighting on the approach to Taliban bastion Sararogha to the east and Kanigurram further south, the army said.

Around 30,000 troops are pitted against an estimated 10-12,000 militants in the semi-autonomous and lawless tribal belt but experts say far more soldiers are needed for a successful counter-insurgency campaign.

More than 125,000 people have been registered since fleeing South Waziristan since October 13, UN refugee agency spokeswoman Arianne Rummery told AFP.

"They join the other 80,500 people which were previously registered. So this means the total registered caseload in terms of families is 28,242, which is around 206,000 people," she said.

Families began fleeing South Waziristan in late May when the military embarked on a campaign of air strikes ahead of the anticipated ground assault, but Rummery said the numbers could go down after verification is complete.

"The volatile security situation constrains our movement," she said.

Apparently trying to distract troops from South Waziristan, militants attacked a Pakistani checkpoint much further north in the lawless tribal belt overnight. The raid in Mohmand killed two troops, officials said Tuesday.

In the capital, a Pakistani brigadier travelling in a military vehicle with his elderly mother escaped assassination Tuesday in Islamabad's second shooting targeting a senior officer in less than a week.

No one was hurt but tensions are high following a spike in violence blamed on Islamist extremists which have left nearly 200 people dead this month.

"Brigadier Waqar Ahmed, who was posted at GHQ (general headquarters), was accompanied by his mother and driver and was going to a local hospital when terrorists fired bullets on him," police officer Khurshid Khan told AFP.

"Luckily all of them survived," he said.

The gunman escaped on a motorcycle, in a near copycat of an attack on an army jeep in Islamabad last Thursday that killed a brigadier on leave from a UN peacekeeping mission and his driver.

Increasingly brazen militant attacks have revealed the extremists' reach across the country and embarrassed the powerful military.

Most audacious was an assault this month on the army's GHQ nerve centre in garrison city Rawalpindi where 10 gunmen kept up a nearly 24-hour siege claimed by the Tehreek-e-Taliban in Pakistan (TTP) movement.