Media playback is unsupported on your device Media caption The BBC's Aleem Maqbool says one soldier survived but is in a critical condition in hospital

Militants in Pakistan have killed at least 20 of the paramilitaries they seized from checkpoints near Peshawar, officials say.

Two men are said to have escaped. One is reportedly in a critical condition.

The troops, from the tribal police force, are reported to have been shot by their captors, who are thought to be from the Pakistani Taliban.

The men were seized following attacks on three checkpoints south of Peshawar, close to the border with Afghanistan.

About 200 armed militants had overrun two of the positions on Thursday, seizing the troops, taking weapons and setting fire to the buildings.

Two tribal police officers were killed in the attacks.

The Pakistani military launched an operation to recover the men and convened a meeting of local tribal elders.

A local government official, Naveed Akbar, said the bodies had been recovered about 4km (3 miles) from where the troops had been abducted.

It is the third attack on targets around Peshawar this month. Suicide bombers launched a raid on the city's airport two weeks ago, killing four people.

Last Saturday a senior politician of the Awami National Party was killed in an attack on a political rally. Seven others died in the blast.

'Peace talks'

On Friday the head of the Pakistani Taliban, Hakimullah Mehsud, released a video in which he offered to open negotiations with Islamabad.

But he refused to lay down his weapons and demanded that Pakistan break ties with the United States before talks could start.

The Pakistani Taliban operates mainly from within the semi-autonomous tribal region along the border with Afghanistan.

The Pakistani government says more than 35,000 people have been killed in attacks blamed on Islamic militants since the attacks of September 11.

It launched an offensive against the group in 2009 in the Swat Valley and South Waziristan, since when attacks by the Pakistani Taliban have decreased.