Pakistani Taliban on Thursday released 17 people after over three months of captivity who mistakenly crossed the border from the country's lawless northwest into Afghanistan, officials said.

More than 30 young people aged between 20 and 30 were kidnapped from Pakistan's Bajaur tribal region during celebrations marking the Muslim Eid holiday in September 2011.

"Today Taliban has released 17 of them, some 8-10 are yet in their custody," Bajaur administration official Islam Zeb told AFP.

Zeb at the time said the boys had been abducted by a militant group allied with Taliban commander Maulvi Faqir Muhammad, who led local insurgents but is believed to have fled to Afghanistan in 2010.

"They have ben freed unconditionally," he added.

Another senior official, Mohammad Tariq Khan, confirmed the release.

Afghanistan shares a disputed and unmarked 2,400-kilometre (1,500-mile) border with Pakistan, and Taliban and other Al-Qaeda-linked militants have carved out strongholds on either side.

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

For years the neighbours have traded accusations over the Taliban and Al-Qaeda-linked militants embedded in both countries, who criss-cross the porous, unmarked border and fight security forces from both governments.

Bajaur was the scene of a major anti-militant operation in August 2008 and in February 2009 and the military said the area had been secured.

Pakistan has for years battled homegrown insurgents in the tribal belt. More than 3,000 soldiers have died but Pakistan has resisted US pressure to do more to eliminate havens used by insurgents.