ISLAMABAD - The Pakistani prime minister lifted a moratorium on the death penalty on Wednesday, a day after Taliban gunmen attacked a school, killing 132 students and nine teachers, a government spokesman said.

Pakistan began three days of mourning on Wednesday for the 141 people killed in the attack on the school in the northwestern city of Peshawar.

The bloodshed has shocked the nation and put pressure on the government to do more to tackle the Pakistani Taliban insurgency. Many people have called in the media for the death penalty to be restored.

"It was decided that this moratorium should be lifted. The prime minister approved," said government spokesman Mohiuddin Wan, referring to Prime Minister Nawaz Sharif's approval of the decision by a ministerial committee.

"Black warrants will be issued within a day or two," he said, referring to execution orders.

He did not give any details about who might be executed under such orders.

A moratorium on the death penalty was imposed in 2008 and only one execution has taken place since then.

There are believed to be more than 8,000 prisoners on death row in Pakistan, about 10 percent convicted of offences labelled "terrorism", said Justice Project Pakistan, a legal aid group.

"Terrorism" has a very broad definition under Pakistani law. About 17,000 cases of "terrorism" are pending in special courts.

Justice Project Pakistan released a report on Wednesday saying that those convicted of terrorism were often tortured into confessions or denied lawyers, and that recent crackdowns had not stopped militant attacks.

"Swathes of defendants whose crimes bear no relation to terrorism have been sentenced to death following extremely unfair trials - whilst terrorist attacks continue unabated," the group said.