At least 12 people, including several children, were killed when mortar shells slammed into a town in northwest Pakistan on Monday, local officials and residents said.
Several shells landed in an open area on the outskirts of Darra Adam Khel, where children were playing and people were watching, they said.
"At least 12 people were killed and six injured, all were civilians," local official Atif Khan told AFP. The casualties were caused by mortar shells, which also damaged some nearby houses, he added.
Nobody claimed immediate responsibility for the shelling.
Security forces denied involvement. "No military operation is currently underway in the area," a security official said, requesting anonymity.
An angry mob of around 200 people protesting against the killings blocked a highway linking the town with Peshawar, the main city in North West Frontier Province, and southern Pakistan.
The town, known for its weapons market, has become a stronghold of Taliban extremists. A Polish engineer, who was beheaded at the weekend, was kidnapped by a Taliban group in the area last September.
Unrest is spreading along Pakistan's northwest border with Afghanistan. Government troops have pressed offensives against Islamist militants in the semi-autonomous tribal region and the once scenic valley of Swat.