A remotely-triggered car bomb claimed the lives of 19 Muslim pilgrims at least in southwest Pakistan Sunday, as three buses carrying about 180 pilgrims were heading to Iran.

A remotely-triggered car bomb claimed the lives of 19 Muslim pilgrims at least in southwest Pakistan Sunday, as three buses carrying about 180 pilgrims were heading to Iran to commemorate the Arbaeen of Imam Hussein (as).

The bomb hit the convoy and set one of the buses ablaze in Mastung district as troops searched for the killers of 21 kidnapped soldiers in the troubled northwest, officials said.

Most of those killed were burnt to death, a senior district government official said. "The bomb was planted in a car. The condition of some of the injured is critical."

There was no immediate claim of responsibility for the bombing at Mastung, some 30 kilometers (18 miles) south of Quetta, the capital of Baluchistan province.

It was the country's second mass killing to be reported in less than a day.

In the northwest, security forces were hunting the killers of 21 soldiers whose bodies were discovered not far from two camps outside Peshawar where they had been kidnapped by the Pakistani Taliban.

Around 200 militants, armed with heavy weapons including mortars and rocket launchers, stormed the government paramilitary camps before dawn on Thursday, killing two security personnel and kidnapping 23.

Officials said Sunday the 21 soldiers had their hands tied with rope before they were shot. Two others -- one wounded and one unhurt -- were also found.

Peshawar is the main city in northwest Pakistan and close to the restive tribal areas bordering Afghanistan, which are regarded as havens for Taliban and Al Qaeda-linked militants.

Mohammad Afridi, a Taliban spokesman from the tribal town of Darra Adam Khel, earlier claimed responsibility for the kidnappings. The Taliban have not yet commented on the killings.

In August the Pakistani Taliban released a video showing what appeared to be the severed heads of a dozen soldiers, after the military said 15 troops had gone missing following fighting with militants in the Bajaur tribal district.

Pakistan has lost more than 3,000 soldiers in the fight against homegrown insurgents but has resisted US pressure to do more to eliminate havens used by those fighting the Americans in Afghanistan.