Mobile phone service is suspended in a number of major cities in Pakistan this weekend, as authorities try to prevent attacks during the Shi’ite festival of Ashura.
Previous bombings have been triggered by the phones.
Security is also being increased.
Dozens of people have died in violence during processions to mark the first month of the Islamic calendar, Muharram.
“Around 468 explosions have occurred using motorcycles and more than 90 percent of blasts have been trigged by mobile phones. We have a record of this,” said Pakistan’s Interior Minister Rehman Malik.
A suicide bomber killed 13 Shi’ite Muslims taking part in a procession in Rawalpindi on Wednesday. A similar attack wounded two police officers on Friday.
Sunni extremists have threatened to target more Shi’ites.