Pakistan is suspending cellphone service in most parts of the country over the next two days to prevent attacks against Shia Muslims during a key religious commemoration, the country's interior minister says.

Militants often detonate bombs using cellphones, and the Pakistani government has implemented similar service suspensions in the past but not on such a wide scale.

Saturday and Sunday are the most important days of Muharram, the first month of the Islamic calendar, which is especially important to Shias.

On Sunday, Pakistani Shias observe the Ashoura, commemorating the seventh-century death of Imam Hussein, the Prophet Muhammad's grandson. The Sunni-Shiite schism over the true heir to Muhammad dates back to that era. Different parts of the Muslim world mark Ashoura on different days — neighbouring Afghanistan, for example, observes it on Saturday.

Sunni extremists often target Shias during Muharram, especially on Ashoura, frequently using cellphones. Several bombings targeting Shiites earlier this week killed over a dozen people.

The suspension of cellphone service will begin at 6 a.m. Saturday and run through the next day, Interior Minister Rehman Malik told reporters in Pakistan's capital, Islamabad. He said 90 per cent of the bombs set off by militants in Pakistan have been detonated using cellphones.

Some commentators have criticized the government for the policy of suspending cellphone service, saying it was a huge inconvenience to millions of Pakistanis and that militants could find other ways to stage attacks.

"The people it truly affects is every other Pakistani who may not have any alternative means of communication," wrote Nadir Hassan in a column Friday in The Express Tribune newspaper.

"These are the people caught in accidents who need to call for help, those who just want to go about their everyday business without being unduly hindered by the state," Hassan said.