They said the incident took place on Thursday after the group of boys, aged between 12 and 18-years-old, visited the area of Gharkhi in Pakistan's Bajaur tribal region for celebrations marking the Muslim Eid holiday.

“These boys inadvertently crossed into Afghanistan while picnicking on the second day of Eid and were kidnapped by militants,” senior local administration official Syed Nasim told AFP.

However, Afghan border police commander General Aminullah Amarkhel said he had no knowledge of the abduction, and the local Taliban commander in Kunar province, where the boys vanished, also said he was unaware of the incident.

Afghanistan shares a disputed and unmarked 2,400-kilometre border with Pakistan, and Taliban and other al Qaeda-linked militants have carved out strongholds on either side.

Another Pakistani administration official speaking anonymously said security forces were stretched thin along parts of the frontier.

“It is a porous border and security cover is not available everywhere,” he said.

Two local intelligence officials said that the kidnappers were apparently from a militant group allied with Taliban commander Maulvi Faqir Muhammad, who led insurgents in Bajaur but is believed to have fled to Afghanistan in 2010.

“The kidnappers were Taliban militants, belonging to Maulvi Faqir Muhammad group,” one official said, on condition of anonymity.