ISLAMABAD, Feb. 7 (Xinhua) -- At least two security personnel were killed and four others injured when their vehicle came under attack in

The incident happened when some unknown militants fired a rocket at the military vehicle, and fled the scene, Dawn News said.

The attack was launched in Mir Ali town of North Waziristan, a semi-autonomous tribal area along Pakistan-Afghanistan border.

No group or person has claimed responsibility for the attack yet.

North Waziristan was once a hotbed of militants belonging to various outlawed organizations. The army removed safe havens of the terrorists from the area by launching an armed offensive "Operation Zarb-i-Azb" in mid-June 2014.

The terrorist incidents have sharply dropped in the whole country following the operation. However, the militants carry out attacks particularly at security forces whenever chance arises for them.

Earlier on Saturday, 11 soldiers were killed and 13 others injured in a suicide attack inside an army unit in the neighboring Khyber Pakhtunkhwa province.