The bomber targeted a gathering of Taliban fighters who were celebrating a three-day truce.
A U.S. drone strike in northeastern Kunar province killed Pakistan Taliban chief Mullah Fazlullah.
SIGAR said in its report that the U.S. needed a new strategy to fight drugs in Afghanistan.
Clashes broke out across Afghanistan despite the start of a government cease-fire, officials said Tuesday.
Taliban leadership may also consider releasing prisoners of war, if they promise not to return to the battlefield.
The U.S. will intensify combat against the ISIS affiliate in Afghanistan during Kabul's halt to attacks on the Taliban.
Afghan President Ashraf Ghani on Thursday announced a weeklong cease-fire with the Taliban.
The suspected Taliban fighters who attacked the Afghan interior ministry Wednesday were wearing old U.S. Army uniforms.
A U.S. rocket artillery strike last week on a gathering of Taliban leaders in Afghanistan killed at least 50 of them.
A suicide bomber struck outside the Afghan Interior Ministry on Wednesday.