Islamabad - A US pilotless drone aircraft was believed to have crashed in Pakistan's tribal region bordering Afghanistan on Saturday, a Pakistani security official said.

"The Americans informed us between 01:00 and 01:30 pm (local time) today that their one drone has crashed due to some technical fault in Angor Adda areas of South Waziristan," a Pakistani military source said on condition of anonymity.

It was the second US drone to crash in Pakistan's tribal region since late last year when the Americans intensified use of pilotless aircraft to target al-Qaeda and Taliban launching cross-border attacks on US forces in Afghanistan.

Pakistan, a key western ally in the international fight against terrorism, has repeatedly protested over the strikes that have eliminated dozens of al-Qaeda's second-tier operatives. (dpa)