In pictures: On Pakistan's tribal frontier

A view of the central square, Chaugalla, in Dera Ismail Khan where the four main streets of the city meet.

The BBC's M Ilyas Khan travelled to Dera Ismail Khan on the edge of Taliban strongholds. More than 500 people have died here since 2007 in bomb attacks and killings blamed on sectarian elements. It is a city of fear. Everything closes by sunset.

A group of Taliban look at a mobile phone

Since 2004, these Sunni hardliners have spread out from South Waziristan and established hideouts in Dera. A sizeable portion of Dera's population is Shia - considered heretical by the Taliban.

Armed militants hanging about close to army patrols is a striking aspect of life. The army prohibits journalists taking pictures of soldiers close to militants. Collaboration became more open after the army supported militants who defied Taliban leaders.

The squatting Taliban guard in the picture is manning a post on a street corner just outside the offices of an anti-Baitullah Taliban group led by Haji Turkistan Bhittani.

This collaboration between the army and militants is also evident in Tank, 60km (37 miles) north of Dera. This guard is manning a post for a group opposed to the Taliban leader. All streets in Tank are patrolled by the army, police and breakaway Taliban.

Haji Turkistan Bhittani (left, wearing a red skullcap)

Haji Turkistan Bhittani (left) has been working against Taliban chief Baitullah Mehsud and has the backing of some in the security establishment. Recently he allied with another group led by Zainuddin Mehsud, who Taliban loyalists killed on Tuesday.

Followers of Zainuddin Mehsud grieve as his body is lowered into the grave in a Dera graveyard

Followers of Zainuddin Mehsud grieved as his body was lowered into the grave in a Dera graveyard which belongs to the Shia community. Burial in his native South Waziristan was not possible as it is controlled by Baitullah Mehsud, who had him killed.

These boys were taken by Zainuddin's men after a tip-off claiming they were on a suicide bombing mission. After his assassination they were locked up in a room. They were shaken when we met them. Their custodian said they were afraid they would be killed.

It is believed that militants loyal to the Taliban leader are among those displaced by regional tension. Local authorities share these fears and police have been known to send back people arriving in the city. For many this feels like inhuman treatment.