At least 17 Pakistani troops have been killed during the ongoing ground offensive against pro-Taliban militants in the country's restive north-west.

The Pakistani army said on Thursday that 17 troopers were killed and at least eight soldiers were injured in an exchange of fire with the militants in the tribal region of South Waziristan.

"It is the first time we have seen such stiff resistance [from the militants]," an army officer, speaking on condition of anonymity, was quoted by AFP as saying.

The clashes erupted as the troops advanced on areas near the militant stronghold of Kanigurram. At least 22 militants were also killed over the past 24 hours, the military added.

The Pakistani army says over 500 militants and around 50 soldiers have been killed since the offensive began on October 17th. The operation has displaced more than 250,000 people and the UN has asked Pakistan to ensure the safety of civilians during the offensive.

In 2009, 1,780 citizens and 780 security officials have been killed in the nuclear-armed country, while the number of the terrorists claimed to have been killed in counter-terrorism operations has reached 5,972.

MMN/SS/MMA