The United Nations' relief program for the flood-ravaged and conflict-ridden northwestern town of Kahr in Bajaur tribal region turned into a bloodbath when a suicide attacker blew up a bomb when more than 1,000 people gathered on Saturday morning to receive free ration.

The food distribution program at the point was being carried out by World Food Program and other aid agencies to help poor people in the conflict-ridden northwestern region of Pakistan when the blast hit the relief center.

Witnesses said more than 40 people were killed and hundreds injured in the bomb attack. I myself have counted 40 bodies but the death toll could rise as several wounded people are in critical condition, Dosti Rehman, an official at the main government hospital in the region, told Reuters news agency.

Amjad Jamal of the World Food Program told CNN that more than 300 people were being screened at the time of the blast and no staff of the program or aid agencies involved were killed.

The traibal region saw intense fighting between Afghanistan's Taliban militants and the Pakistani army which is pursuing them. The attack on innocent civilians came a day after 11 soldiers and 24 militants were killed at a checkpoint in the neighboring Mohmand region. Though no outfit has claimed responsibility so far, the suspicion is on the Taliban militants in the region.

Earlier this month 40 people were killed in Mohmand region which also witnessed the worst suicide attack in July that killed more than 100.