Plagued by mounting attacks by Islamist militants loyal to al-Qaeda, Pakistan now faces a second wave of violence as its minority Shia Muslims prepare for their annual mourning period.
The 40-day Shia mourning period, expected to begin tomorrow, has become a lightning rod for sectarian violence and comes as the country is still reeling from the assassination of opposition leader Benazir Bhutto in a gun and bomb attack.
The Interior Ministry said 35 districts in the country had been declared "sensitive" and all security agencies had been put on high alert to avert sectarian violence during the mourning period, known as Moharram.
"We appeal to all citizens to exercise vigilance and extend full cooperation to the security agencies," said ministry spokesman Javed Iqbal Cheema.
Moharram marks the death anniversary of Imam Hussein, a grandson of the Prophet Mohammad, who was killed in a battle with political rival, Yazid, in 680 ADin the Iraqi city of Kerbala.
The climax of Moharram is the tenth day, known as Ashura, when worshippers flog themselves with steel-tipped flails or slash their bodies with knives to express solidarity with Hussein.
Moharram processions have come under attack by Sunni sectarian militants in recent years.
Pakistan saw a surge of religious violence in the 1980s with the emergence of militant groups, most of them Sunni, funded by the United States and Saudi Arabia to fight Soviet forces in Afghanistan and Shia radical groups following the success of the 1979 Islamic revolution in Shia Iran.
While ordinary Sunni and Shia Pakistanis live side-by-side, radicals from the two sects have inflicted a bloody toll in tit-for-tat assassinations and bomb attacks since then.
Last year, a suicide bomber blew himself up among policemen escorting a Moharram procession in the northwestern city of Peshawar, killing 11 people, most of them policemen.
In 2006, about 40 people were killed in suicide attack on an Ashura procession in the town of Hangu.
The attacks were blamed on Sunni sectarian militants, many of whom established links with al-Qaeda after President Pervez Musharraf forged a security alliance with the United States following the September 11th attacks in 2001.
The Interior Ministry is particularly worried about attacks in the North West Frontier Province (NWFP) on the Afghan border, where militants are active.
Shia leaders said they were ready to cooperate with the government to ensure security but opposed any move to restrict their processions. "Concern about terrorist attacks cannot be overlooked," Sajid Ali Naqvi, a senior Shia cleric and a vice president of country's main Islamic party alliance said.