In a statement on Friday, Mousavi expressed sympathy with the Afghan nation and government as well as the families of the victims of the inauspicious terror attack, which martyred and wounded dozens of people.
The gathering attended by senior Afghan figures, including Chief Executive Abdullah Abdullah, came under gun and rocket attack earlier today.
The attack, which killed at least 29 people and wounded more than 55 others, was the first major attack on the Afghan capital since the US reached a troop withdrawal agreement with the Taliban.
