Pakistani Shi'ites called on the military on Sunday to take control of the city of Quetta after a bombing by Sunni militants killed 85 people, and threatened to stage a long march to the capital if their demands were not met.
Pakistani leaders have done little to contain hardline Sunni Muslim groups which have stepped up a campaign of bombings and assassinations of minority Shi'ites in a bid to destabilize the nuclear-armed country and install a Sunni theocracy.
The unpopular government, which is gearing up for elections expected within months, faces growing anger for failing to deliver stability.
On Saturday, Lashkar-e-Jhangvi (LeJ), seen as the most ruthless Sunni sectarian group, claimed responsibility for the Quetta attack, which deepened suspicions among Shi'ites that Pakistan's intelligence agencies were turning a blind eye to the bloodshed or even supporting extremists.
The families of the some of the victims have said they will not bury their dead until the army steps in to protect Shi'ites, said Hasnain Zaidi, a spokesman for an alliance of Shi'ite groups called Majlis Wahdat al Muslimeen.
Muslim tradition requires that bodies are buried as soon as possible and leaving them above ground is a potent expression of grief and pain.
"The situation is very tense," Zaidi told Reuters. "Thirty five bodies were burned beyond recognition. Shi'ite families will hold a long march to Islamabad if the army does not step in."
The death toll from the bombing rose overnight, with most of the casualties in the main bazaar of the southwestern city, the capital of Baluchistan and near the border with Afghanistan. The attack targeted ethnic Hazara Shi'ites.
"The terrorist attack on the Hazara Shi'ite community in Quetta is a failure of the intelligence and security forces," Nawab Zulfiqar Ali Magsi, governor of Baluchistan province, said while touring a hospital.
Leaders of the Hazara community called on the government to take decisive action, and Pakistanis warned that sectarian violence was spiraling out of control ahead of elections expected in May.
"The government is responsible for terrorist attacks and killings in the Hazara community because its security forces have not conducted operations against extremist groups," said Aziz Hazara, vice president of the Hazara Democratic Party.
"We are giving the government 48 hours to arrest the culprits involved in the killing of our people and after that we will launch strong protests."
On Sunday, people searched for survivors under blocks of cement torn off buildings by the blast. A large blood stain could be seen on a wall near the site.
Many shops and bazaars were closed. Relatives of the wounded responded to an appeal for blood made by hospitals.
"The government knows exactly who is doing what and who is behind all this," said Mohammad Imran, a local trader. "If the government wants (to prevent it), no one can take even a kitchen knife into any market."
In the capital Islamabad, about 400 people, including some Sunnis, staged a protest demanding the government stamp out extremism. Protests were also held in other cities, including the commercial capital Karachi.
"There is a law of the jungle, but in this country I think there is not even a law of the jungle," said Syed Abbas Naqvi, a Shi'ite.
"A person who is extremely helpless, vulnerable and powerless is always made the target of barbarity whereas all brutal people like the terrorists, Taliban and others who carry out these merciless acts...roam free all over the country."
POVERTY, CORRUPTION, POWER CUTS
Public anger has been growing over a host of other issues as well in the run-up to elections, from widespread poverty to power cuts to corruption.
Critics say Pakistan's intelligence agencies previously supported groups like LeJ to fight against Indian forces in Kashmir and failed subsequently to control them.
Now Shi'ites in Quetta and other cities say they are under siege by the al Qaeda-linked LeJ, which has also attacked Shi'ites in other parts of the country in recent months.
"We have grown tired of picking up the bodies of our loved ones," said Nasir Ali, 45, a government employee. "I have lost three family members so far in such blasts."
LeJ has also said it was behind a bombing last month in Quetta which killed nearly 100 people, one of Pakistan's worst sectarian attacks.
Sectarian violence is piling pressure on the U.S.-backed administration to avert a major conflict between Sunnis and Shi'ites.
"Unless we decide to unite, we will continue to get killed, said Malik Afzal, a Sunni student. "Today they (Shi'ites) have died. Tomorrow we (Sunni Muslims) will die. The next day, others will get killed."
More than 400 Shi'ites were killed in Pakistan last year, many by hitmen or bombs. Some hardline Shi'ite groups have struck back by killing Sunni clerics.