The boys mistakenly crossed the border from Pakistan to Afghanistan while picnicking, officials say [GALLO/GETTY]

Taliban fighters have kidnapped more than 30 Pakistani boys who had mistakenly crossed the unmarked border in the country's lawless northwest into Afghanistan, officials said.

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

"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.

Islam Zeb, a Bajaur administration official, said the boys had been abducted by fighters allied with Taliban commander Maulvi Faqir Muhammad, who led  insurgents in Bajaur but is believed to have fled to Afghanistan in 2010.

"The kidnappers belonged to Tehreek-e-Taliban Pakistan's (TTP) Faqir Muhammad group, which used to operate in Bajaur," said Zeb.

Afghanistan shares a disputed 2,400km border with Pakistan, where Taliban fighters are believed to reside.

Another 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.

The last similar incident was in June 2009 when hundreds of Pakistani  students from the tribal North Waziristan region were kidnapped by Pakistani Taliban as they travelled in a convoy of buses to the northwestern town of  Bannu after their college closed for its summer vacation.

All were later released unharmed.

Afghanistan and Pakistan blame each other for several recent cross-border attacks that have killed dozens and displaced hundreds of families.

Source: Agencies