At least four security personnel were killed and five others injured in a rocket attack launched Saturday by unknown militants in Pakistan\'s northwest tribal area of North Waziristan which borders Afghanistan. A convoy of Pakistani security forces patrolling in a village in Spina, North Waziristan came under rocket attack, reported local Urdu TV channel Express. Three rockets were fired at the convoy and four security personnel were killed on the spot and five others injured in the attack have been shifted to nearby hospital. No group has claimed responsibility for the attack. North Waziristan is considered one of the safe havens for militants to launch cross-border attacks on the U.S.-led coalition forces and Afghan army in Afghanistan. Pakistan has carried out a number of military operations against the militants hideout in northwest tribal areas such as Orakzai, Kurram and Bajaur.