Umar, a bomber who took part in a suicide mission that killed more than 40 people at a Sufi shrine sought forgiveness on Friday during investigation.

The boy, who police said is 14, was arrested after his belt of explosives failed to go off in Sunday's attack.

He said he had been trained by militants close to the Afghan border, and that his handlers spoke of "more than 200 other boys going through the training."

In the attack on the Hazrat Sakhi Sarwar Darbar, at least two bombers successfully detonated explosives, killing at least 44 people.

The boy whose explosives didn't go off was arrested shortly after the incident.

In an interview, he said he is "seeking forgiveness" from the families of those killed and wounded.

"I never knew that I was going to hurt Muslims. I learned it only after I failed," said the boy. "May Allah forgive me."

Umar said he spent two months training with four other boys in the town of Mir Ali in North Waziristan.