QUETTA, Pakistan (AFP) ― A car bomb killed at least 19 Shiite Muslim pilgrims in southwest Pakistan on Sunday as troops searched for the killers of 21 kidnapped soldiers in the troubled northwest, officials said.

The remotely-triggered bomb hit a convoy of three buses carrying about 180 pilgrims to Iran and set one of the buses ablaze in Mastung district, they said.

“At least 19 people have been killed and 25 injured,” said Tufail Baluch, a senior district government official. “All of them were Shiite pilgrims.”

Most of those killed were burnt to death, he 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 south of Quetta, the capital of Baluchistan province.

The province has become an increasing flashpoint for sectarian violence between Pakistan’s majority Sunni Muslims and minority Shiites, who account for around a fifth of the country’s 180 million people.

Baluchistan is also rife with Islamist militancy and home to a regional insurgency which began in 2004. The insurgents demand political autonomy and a greater share of profits from oil and gas resources.

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.