Sixty-nine people, including women and children, were killed and nearly 200 injured when a powerful bomb ripped through a Shia neighbourhood of Quetta city in southwest Pakistan today, the latest in a string of attacks targeting the minority community.

The blast occurred at Kirani Road in Hazara Town, a suburb of Quetta with a large Shia population that has been targeted by terrorists in the past.

The area was crowded at the time of the blast.

The bomb was hidden in a vehicle and triggered by remote control, DIG Wazir Khan Nasir told reporters.

He said the Shia Hazara community was the target of the attack.

The death toll rose to 69 after several bodies were pulled out the rubble of a two-storey building that collapsed.

About 200 injured were taken to three hospitals. Several women and children were among the dead.

Officials said the vehicle with the bomb was parked near the pillar of a building in a market. The building collapsed due to the intensity of the blast.

An estimated 100 kg of explosives was used in the attack, officials said.

"The blast was so intense that it razed a two storey building to the ground and they are still some people trapped under the debris which is being cleared in a extensive rescue operation," Quetta's city police chief Mir Zubair told PTI.

A spokesman for the banned extremist group Lashkar-e- Jhangvi claimed responsibility for the attack.

Footage on television showed several buildings were reduced to piles of rubble by the blast that was heard all over Quetta, the capital of the restive Balochistan province.

Several shops and vehicles were also destroyed. Angry people took to the streets and protested against the attack.

The protesters pelted vehicles with stones and prevented rescue workers and police from approaching the site of the blast for some time. They also blocked roads and fired in the air.

Security forces cordoned off the area and did not allow the media to approach the site of the blast.

Officials said this was done as terrorists had set off a bigger bomb after a smaller initial blast in recent attacks.

Similar attacks in the recent past have also been blamed on the banned Lashkar-e-Jhangvi, a notorious militant group that often targets Shias.

On January 10, a twin suicide attack in Quetta killed 92 Hazara Shias and injured over 100, the highest toll in a single attack on Shias, who make up 20 per cent of Pakistan's population of 180 million.

Following the attack, the federal government imposed Governor's Rule in Balochistan.

President Asif Ali Zardari telephoned Balochistan Governor Zulfiqar Magsi and directed him to personally oversee rescue and relief operations.

Zardari further said all possible steps should be taken to protect the Shia Hazaras.

Zardari and Prime Minister Raja Pervez Ashraf condemned the attack and reiterated the government's resolve to continue the fight against militants.

"We will not be intimidated by such cowardly acts and such acts will not deter our resolve to fight terrorism," Ashraf said.

Shia groups and political parties asked people to observe three days of mourning and called for a strike in Quetta tomorrow to protest the killing of members of the minority community.

The Balochistan government announced a day of mourning tomorrow.

Governor Magsi said the seriously injured would be flown in military aircraft to Karachi for treatment.

He announced a reward of Rs 10 million for anyone who provides information about the perpetrators of the attack.