Pakistan suspended mobile phone services in major cities on Friday to prevent terror attacks from marring commemorations for the holy month of Muharram, officials said.
Mobile and wireless phone services were temporarily blocked in the commercial capital Karachi, the southwestern city of Quetta and in parts of the capital.
It is the second time Pakistan has shut down mobile networks during Muharram, which culminates with Ashura, the holiest day in the Shiite Muslim calendar when faithful march to mourn the seventh-century killing of Imam Hussein.
A suicide bomber killed 23 people and wounded 62 others at a Shiite procession in Rawalpindi on Thursday, the deadliest bombing in Pakistan for five months.
Ashura falls this year on Sunday and has been a magnet for sectarian attacks with rights groups heavily criticising the government for failing to stop extremist violence.
"We have shut our service in Karachi and Quetta on the instructions of the Pakistan Telecommunications Authority from 1:00 pm (0800 GMT) to midnight," said an official at Mobilink, the country's largest mobile phone service provider.
An official at PTCL, which runs the only landline and wireless phone services in Pakistan, said wireless phones had also been turned off at the government's instructions.
Interior Minister Rehman Malik announced the phone suspension earlier, saying it was intended to "ensure security during and after the Muharram processions".
Southern province Sindh, where Karachi is the capital, also declared Friday a public holiday for security reasons.
Most businesses and shops were closed in the city and roads were deserted.
In December 2009, a suicide bomber killed 43 people in Karachi at a Shiite procession to mark Ashura.
Pakistan says 35,000 people have been killed as a result of terrorism since the 9/11 attacks and the 2001 US-led invasion of neighbouring Afghanistan.