Five Afghans died and four more were wounded when a suicide bomber disguised as a woman blew himself up at an army checkpoint in eastern Afghanistan.

Police said on Thursday that the blast was in Khost province the day before.

Afghan soldiers were checking a vehicle when the bomber, sitting in the backseat, set off a bomb hidden under a burqa shroud, said Mohammed Ayub, the regional police chief.

The blast killed three soldiers, the driver of the car and a farmer working in a field nearby.

Police didn't know if the driver was involved in the bomber's plans or was an innocent victim.

The explosion was originally reported by police on Wednesday as having been caused by a landmine.

Ayub blamed the Taliban for the attack.

"The bomber probably wanted to go into Khost city for a suicide attack there, but panicked and blew himself up when the soldiers started checking," the Associated Press quotes him as saying.

Suicide bombings are relatively new to Afghanistan.

The governor of Nimroz province said on Thursday that al-Qaeda militants are coming to Afghanistan from Iraq, many on orders to carry out suicide attacks.

"There is a big group coming from Iraq," Nimroz provincial Gov. Ghulam Dusthaqir Azad said in an AP report after interrogating an Iraqi caught sneaking into the country. "They're linked to al-Qaeda and fought against U.S. forces in Iraq. They have been ordered to come here. Many are suicide attackers."