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.