A roadside bomb killed at least seven people near a Shi'ite procession in Pakistan on Saturday, police said, while security forces are on high alert over fears of large-scale sectarian attacks on the minority sect across the country.
Pakistan, a nuclear-armed U.S. ally, is suspending phone coverage in many cities this weekend, an important one in the Shi'ite Muslim calendar, after a series of bomb attacks on Shi'ites triggered by mobile phones.
Hardline Sunnis have threatened more attacks as the Shi'ite mourning month of Muharram comes to a climax. More than a dozen people have already been killed this week observing Muharram.
Saturday's attack occurred in the city of Dera Ismail Khan in Pakistan's northwest, a stronghold of al-Qaeda-linked Sunni militant groups who regard Shi'ites as non-Muslims and have stepped up sectarian attacks in a bid to destabilize Pakistan.
Four children were among those killed by a 8-10 kg bomb set off by a television remote control device because cellphones were not operational, police said. Pakistani television stations showed footage of children in hospital beds, who were among 17 wounded.
Intelligence information indicates more attacks have been planned for the coming days in the capital city of Islamabad, Karachi and Quetta. Mobile phone service will be suspended for hours in the three cities and dozens of others over the weekend.
In Karachi, more than 5,000 police are expected to patrol the streets during Muharram events over the next two days, with hundreds more on alert.
Muharram marks the anniversary of the Battle of Karbala, where the grandson of the Prophet Mohammad and his family members were killed.
Western intelligence agencies have mostly focused on anti-American groups like al Qaeda and the Taliban in Pakistan, paying far less attention to sectarian hardliners who are becoming an increasing deadly and effective force.
Pakistani intelligence officials say extremist groups led by Lashkar-e-Jhangvi have intensified their bombings and shootings of Shi'ites in the hope of triggering conflict that would pave the way for a Sunni theocracy in U.S.-allied Pakistan.
The schism between Sunnis and Shi'ites developed after the Prophet Muhammad died in 632 when his followers could not agree on a successor.
Sunnis recognise the first four caliphs as his rightful successors. The Shi'ites believe the prophet named his son-in-law Ali. Emotions over the issue are highly potent in modern times, pushing some countries, including Iraq five years ago, to the brink of civil war.
Pakistan is nowhere near that stage but officials worry that LeJ and other groups have succeeded in dramatically ratcheting up tensions and provoking revenge attacks in their bid to topple the U.S.-backed government in nuclear-armed Pakistan.