A suicide bomber attacked a gathering of people receiving aid in northwest Pakistan on Saturday and at least 40 people were killed and 70 injured, officials said.
Local police official Fazal-e-Rabbi said the bomber, dressed in a traditional women's burqa, first lobbed two hand grenades into the crowd gathered at a checkpoint outside the food center in the town of Khar on Saturday.
Rabbi said the attacker, who is believed to be a woman, then detonated an explosive vest. If true, it would be for the first time that a woman has carried out a suicide attack in the tribal areas of Pakistan.
"First there were two small explosions and people started running for cover. But within seconds there was a major blast and there were dead bodies scattered everywhere," witness Hussain Ahmed said. "It was very terrifying."
A crowd had cleared a checkpoint and members were awaiting their turns at a United Nation's World Food Program distribution center in Bajaur Agency headquarters, Khar, near the Afghan border, NBC News said.
"The attack took place when hundreds of people were gathered to receive food rations for people displaced by fighting," Wisal Ahmed, a government official in the Bajaur region on the Afghan border told Reuters news agency.
Wounded in critical condition
"I myself have counted 40 bodies but the death could rise as several wounded people are in critical condition," Dosti Rehman, an official at the main government hospital in the Bajaur region on the Afghan border told Reuters.
A hospital doctor in Khar said some of the seriously injured people had been sent to other hospitals at the nearby Dir district and Peshawar for better treatment due to lack of doctors and medicines in the tribal region.
"There are injured people lying everywhere and crying of injuries. Some lost their lives due to lack of timely healthcare," the doctor said.
Khar authorities appealed over loudspeakers for doctors and paramedics to go to the hospital with many health workers on leave for a public holiday.
Islamist militants battling the state have attacked buildings handing out humanitarian aid in Pakistan before, presumably because they are symbols of the government and Western influence. A suicide bomb killed five at a WFP office in Islamabad on Oct. 4.
But those waiting for food rations included hundreds of people from the Salarzai tribe, who may have been the target.
Many had been forced from their homes by earlier fighting between security forces and al-Qaida-linked militants.
Anti-Taliban tribeThe Salarzais are a major regional anti-Taliban tribe, which has been backing army operations against the militants.
Pakistan's volatile ethnic Pashtun tribal lands on the Afghan border have been infested with militants and the army has mounted a series of operations to dislodge them.
Salarzai tribesmen have been instrumental in raising lashkars, or tribal militia, to back the government's operations against the militants.
Militants have attacked pro-government tribes in the past to punish them for supporting the government.
The government has declared victory against the Taliban in Bajaur tribal region and claimed to have killed more than 2,500 militants during military operations launched Aug. 6, 2008.
On Friday, 46 militants surrendered to the government through a jirga, or tribal council, of local elders in Siddiqabad area near Khar.
However, in the neighboring agency of Mohmand, to the south of Bajaur, 150 Islamist militants attacked five security posts Friday in an unusually large and coordinated assault, sparking hours of fighting that killed 11 soldiers and 24 insurgents, officials said.
A Taliban spokesman confirmed clashes but disputed the official death toll saying only two of their fighters were killed.