At least 17 people have been killed and dozens more wounded after an explosion in Pakistan's Khyber tribal area, officials say.

The explosion took place in the Jamrud district on Monday morning, and wounded more than 50 people, said Azam Wazir, a local administration official.

Al Jazeera's Kamal Hyder, reporting from the Khyber Agency, said "the attack is said to have taken place in a time when the bazaar was jam-packed with people".

Wazir said that an explosives-laden vehicle had been parked outside the office of the Khyber's political agent, the area's top civilian administrator.

Five Afghan women and three children were among the dead, he said.

Officials at the local hospital told Al Jazeera that the death toll was expected to rise, as several of the casualties were in critical condition.

Pools of blood and charred pieces of human flesh littered the roadside, along with at least 20 burnt vehicles, said a reporter for the AFP news agency. Clothes, school books, children's and shoes lay everywhere.

Taj Muhammad, 40-year-old area driver, said he was entering Jamrud when he heard the explosion and saw a ball of fire.

"I rushed to the site and saw people engulfed by flames. There were pieces of human flesh and blood everywhere. I saw a little child who was injured and crying. I took this boy to hospital," he told the AFP news agency.

"When I picked up the injured boy he looked like my son and I was really so

Pakistani television news channels broadcast pictures of wrecked cars and pick-up trucks damaged in the blast, which took place near rows of shops. Also nearby was a bus stop, where passengers wait for buses to take them across the northwest and to other parts of the country.

Residents threw buckets of water on burning vehicles as rescue workers transported the wounded to the hospital.

There was no immediate claim of responsibility for the attack, but our correspondent said "there were suspicions and concerns by the political agency that this could be a reaction to the ongoing military operations by the pakistani forces and the Khyber agency".

Quetta sectarian attack

Meanwhile, in the southwestern city of Quetta, police said that gunmen had killed a provincial government spokesperson and two policemen in an apparent sectarian attack.

Hamid Shakeel, a police official, said that the attackers shot dead Khadim Hussain Noori on Monday in the capital of Balochistan province.

Noori was the director of the public relations department of the provincial government.

Shakeel said that the gunmen killed two policemen and wounded a third as they made their escape on a motorcycle.

Balochistan has seen a spike in sectarian killings in the past year, as extremist groups have targeted minority Shia Muslims.

Source: Al Jazeera and agencies