A roadside bomb killed at least seven people near a Shia procession in Pakistan.
Pakistan is suspending phone coverage in many cities this weekend after a series of bomb attacks on Shias were triggered by mobile phones.
Hardline Sunnis have threatened more attacks as the Shia mourning month of Muharram comes to a climax.
More than a dozen people observing Muharram have already been killed this week .
Today's attack occurred in the city of Dera Ismail Khan in Pakistan's northwest.
This area is a stronghold of al-Qaeda-linked Sunni militant groups who regard Shias as non-Muslims.
They have stepped up sectarian attacks in a bid to destabilise Pakistan.
Four children were among those killed by a 8-10kg 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.
Sunnis recognise the first four caliphs as his rightful successors.
The Shias 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 government in nuclear-armed Pakistan.