Updated

Pakistani Prime Minister Nawaz Sharif has asked the country's president to reject a petition for pardon for four suspected militants sentenced to death over the Peshawar school attack last December that killed 150 people, mostly children.

The horrific Dec. 16 attack was claimed by the Taliban and prompted Pakistan to lift a 2008-moratorium on the death penalty.

The government released a statement on Thursday quoting Sharif as saying that the "brutal and merciless killings" of the children in Peshawar have convinced him that the perpetrators of such crimes don't deserve any mercy.

Under the constitution, Pakistan's president has the authority to pardon any convicted person.

Since the moratorium was lifted, Pakistan has hanged nearly 300 on death row, most of them convicted criminals — not the Taliban or other insurgents.