Islamabad, January 20 (RHC)-- Terrorists raided a university in northwest Pakistan on Wednesday, apparently timing their attack to a ceremony at the school to ensure maximum casualties.

After security forces combed the campus block by block after the massacre, Pakistani officials said at least 20 civilians were killed, along with four terrorists.

The attack took place at Bacha Khan University in Charsadda, Peshawar, less than 40 kilometers from where the Pakistan Taliban killed 145 people, including 132 children, in a school attack in December 2014.

One Pakistan Taliban spokesman, Umar Mansoor, said the attack was in retaliation for military operations against the group. Mansoor was also the mastermind behind the December 2014 attack, Pakistan's DawnNews reported.