Pakistan suspended mobile phone networks in major cities on Friday and many schools were closed as Islamist groups protested for a third day against the acquittal of a Christian woman facing the death penalty for blasphemy.

The Supreme Court on Wednesday overturned the conviction of Asia Bibi, a mother of five, and ordered her freed. She had been living on death row since 2010 after being convicted under Pakistan's tough blasphemy laws.

The Supreme Court decision enraged hardline Islamists, in particular members of a group called the Tehreek-e-Labaik (TLP), who have taken to the streets to call for the death of the judges who made the decision and the ouster of the government.

Authorities, including members of the main military security agency, held negotiations with the leader of the group late on Thursday but they came to no agreement, the TLP leader, Khadim Hussain Rizvi, said.

The spokesman for the military said the armed forces hoped the "matter is resolved without the disruption of peace".

"Both sides should talk amongst themselves, and we should not reach the stage where this matter comes under the ambit of the armed forces," he told state-run PTV channel.

On Friday, telephone networks were down in the capital, Islamabad, and the eastern city of Lahore, where pockets of TLP protesters blocked main roads.

"All services have been shut down by the government,” said a customer service representative at one of Pakistan's main mobile phone companies, while declining to elaborate.

Authorities in Pakistan often shut down mobile phone networks in the hope of distrusting the organisation of protests.

Schools across the most populous province of Punjab were closed.

In the commercial hub of Karachi in the south, normally bustling markets were shuttered.

A Reuters photographer saw about 100 protesters using stones, pieces of wood and motor-bikes to create a barricade across one main road.

Bibi's whereabouts were not known on Friday. Her family has been in hiding this week.