The U.S. envoy for Afghan peace Ambassador Zalmay Khalilzad strongly reacted to the attack on Amrullah Saleh’s office in Kabul.

Ambassador Khalilzad said in a Twitter post that “The attack on Amrullah Saleh’s political party offices was grotesque and a clear act of terrorism.”

Futhermore, Ambassador Khalilzad said “We condemn it in the strongest terms. The perpetrators should be brought to justice.”

He also added “We stand with Afghanistan in the fight against terror.”

No individual or group including Taliban has so far claimed responsibility for the attack.

A group of militants launched the attack late on Sunday afternoon by detonating a car packed with explosives.

Nasrat Rahimi, a spokesman for the Ministry of Interior said the attack killed 20 people and wounded at least 70 others.