The shootout erupted on Monday when members of one clan diverted water from a canal near Parachinar town in the tribal Kurram region and attacked farmers from a rival tribe when they demanded a share.

"Five people are confirmed dead," local administration chief Mohammad Saleem Khan told AFP.

Residents however put the toll at 12 dead and 31 wounded.

"Rival tribes are perched on the hilltops and heavy firing is still going on," a resident said on condition of anonymity.

Khan said authorities had arranged a council of tribal elders to resolve the situation.

"The jirga (council) has gone to the site of the clash to convince the armed men to come down from the hills," he said.

"We hope a ceasefire will be arranged later in the day."

Reuters adds: Pakistani authorities sent troops to a remote region on the Afghan border on Tuesday to end clashes over scarce water after five people were killed.

Pakistan faces a serious water shortage this year after light rain and snow over the winter. Water rights are a divisive issue in many parts of the country, but the clashes in the Kurrum region are the most serious this year over the resource.

Violence erupted on Monday when people of one clan tried to divert water from an irrigation canal to their fields and men from another clan resisted.

The rivals battled with rifles, mortars and rocket-propelled grenades and five people were killed and 27 wounded, said the region's administrator, Mohammad Salim Khan.