Clashes between rival Shia and Sunni groups in a tribal region in north-western Pakistan have intensified after Taliban fighters infiltrated the area to back one of the factions.

The violence, which has left at least 15 people dead and nearly 50 injured in Kurram Agency since the weekend, has further spread after Taliban militants entered the area from nearby tribal regions.

The civil administration of the Federally Administered Tribal Areas has sought more troops to control the situation, media reports said on Wednesday.

A 16-member peace 'jirga' or a council, which was sent to Kurrum Agency to broker a peace deal, held talks with tribal elders to calm down the situation but failed to finalise a truce. It may now be reconvened in a fresh bid to broker a truce, officials said.

Despite curfew being in place in Parachinar, the headquarters of Kurram Agency, and nearby areas, heavy clashes were reported from several places.

In the Balishkhel area, the rival groups set houses on fire, displacing a large number of people. Hundreds of armed Taliban fighters set two religious buildings on fire in Sadda, a city near Parachinar, The Post reported.

They also attacked residential complexes with sophisticated weapons, causing heavy damage.

The local administration has also said that it would be "impossible" to organise peaceful elections in the area due to the violence.

Eyewitnesses said the rival groups are using mortars, missiles and rocket launchers while the army is targeting their positions with artillery in a bid to stop the fighting.

The local people are facing difficulties as curfew has not been lifted for the past four days and all roads in the region have been closed for almost 40 days.

This has cut off the supply of fuel, medicines and food from the North West Frontier Province to Kurrum Agency.

Students too have been hit by the closure of educational institutes.

Since mid-November, clashes between Shia Turi tribesmen and their Sunni Mengal rivals have claimed over 180 lives and left more than 400 injured.

The fresh fighting erupted over the weekend after a group of armed men looted and set on fire houses and shops belonging to a rival sect in Parachinar.