Islamabad, May 4 (IANS): Fifteen people were killed and 40 wounded when a suicide bomber walked into a market and triggered a massive explosion in Pakistan's northwest, a media report said.

The attacker targeted security forces conducting checks at Khar Bazaar in Bajaur Agency, part of the Federally Administered Tribal Areas, Geo News reported.

Panic spread in the area after the deafening blast led to the collapse of several shops.

A senior official said it was a suicide attack and four policemen were among the dead.

The bomber was on foot and detonated his explosive vest when he reached close to a police check post, sources added.

Xinhua cited TV reports as saying that curfew had been imposed in the area.

No group has as yet claimed responsibility for the attack.

The attack took place just two days after May 2, a day which marked a year after Al Qaeda chief Osama bin Laden was gunned down by US special forces in Abbottabad town.