A bomb exploded near the Afghan Interior Ministry compound in Kabul minutes before gunmen exchanged fire with the security forces, resulting in the killing of one police official.
Just after midday, a auto bomb exploded at the entrance to the ministry compound, said Hashmat Stanekzai, spokesman for Kabul police.
According to police, the attackers used two armored SUV vehicles - one Land Cruiser and a Ford - to get through check points. Two militants then detonated suicide bombs, allowing the others to pass through a gate at the ministry.
Islamic State has claimed many attacks in Kabul but Afghan security officials doubt the claims and say numerous attacks are much more likely to be the work of the Haqqani network, a group affiliated with the Taliban which has proven expertise in mounting urban attacks.
Gen. Nicholson expressed concern that Afghan troops seeing people wearing United States uniforms and driving a U.S. vehicle might "hesitate", but that immediate engagement was exactly what the Afghan forces were supposed to do.
The Taliban are also stepping up their assaults on the capital, making the heavily fortified city the deadliest place in the country for civilians. The attackers did not manage to enter the main compound.
IS, which is trying to make inroads in Afghanistan, claimed responsibility for the attack via its Amaq propaganda service.
The militants were also threatening to overrun parts of Takhar province in the country's north this week, claiming to have seized arms and equipment after seizing police checkpoints in the besieged Kwajah Ghar and Dasht-e Qalah districts along the Tajikistan border.
They were captured for different reasons ranging from cooperating with Afghan security forces to being a member of the local police force, Saleem said.
The U.S. military said the May 24 meeting involved commanders from different Afghan provinces, including neighboring Farah, where Taliban fighters briefly threatened to overrun the provincial capital this month.
"The attackers had long hair and started shooting at police force members", said Mohammad Salim, a police soldier. He said the victims included mechanics who had been contracted to fix Afghan army vehicles.