Two children were killed and another critically wounded in an accidental grenade explosion near Khyber Pakhtunkhwa's Swat Valley on Sunday, officials said.

The children of a shepherd family were playing in a mountainous village in Buner district when they found the hand grenade and accidentally set it off, local government official Zariful Maani told AFP.

The two brothers, aged nine and 10, died, while their seven-year-old female cousin is in critical condition, Maani said.

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Another local government official, Aizaz Ahmad, confirmed the details.

School-going children remain caught up in the years-long conflict between security forces and militants in the region following a Taliban insurgency in the area since 2007.

In the beginning of 2007, Taliban militants led by Maulana Fazlullah, now central chief of the Tehreek-i-Taliban Pakistan (TTP) took control of the Swat district and waged a campaign of attacking schools, killing policemen, and beheading opponents.

However, Pakistani officials say that Fazlullah fled to Afghanistan during an offensive the military launched in 2009. Despite the operation, the Taliban targeted schoolgirl Malala Yousafzai in 2012.