The National Directorate of Security said on Sunday the three suicide bombers who detonated explosives during Saturday’s funeral of Salem Ezadyar had hidden the triggers for the explosives in their shoes.

An NDS source said three detonated their devices while a fourth suicide bomber was arrested.

According to the NDS, the suicide bombers had been trained at Mawlawi Ahmad Madrassa in Chaman, Quetta, in Pakistan and sent to Afghanistan to carry out the attack.

The suicide bombers killed at least 20 people and wounded over 80 on Saturday during the burial service for Salem Ezadyar, the son of a senator.

Ezadyar had been killed on Friday during the mass rally in Kabul when police opened fire on demonstrators, killing at least five.

The Taliban on Saturday rejected claims of involvement in the attack.