Authorities in Afghanistan say militants attacked a government security building in Kabul on Tuesday, detonating a suicide car bomb.
It happened during the morning rush hour, with the attackers then exchanging gunfire with Afghan security forces.
Just a few hundred metres away, the country's President, Ashraf Ghani, released a statement condemning the incident.
Pictures from the scene showed the windows blown out of an office that houses a National Directorate of Security unit.
The Health Ministry says civilians and members of the Afghan security forces were also caught up in the attack.
These witnesses described what happened.
"While I was working there was a big blast, dust covered the whole area. I couldn't see what was happening, later I could see a lot of damage."
"While I was inside my office, a very big explosion happened. It damaged the wall and there was glass everywhere. There are some suicide attackers in the area."
Reports say at least 28 people have been killed, and more than 320 have been wounded.
It is believed to be the deadliest single attack in the city in five years.
A surgical doctor treating victims, Yarbaz Khan, says the country's medical services are coping.
"We received nineteen wounded, some of them in serious condition. We have hospitalised 10 wounded here. Our services are ready to treat their injuries."
On its website the Taliban says it has carried out an attack on "Department 10", a unit responsible for looking after government ministers and other VIPs.
The bombing reignites fears violence in Afghanistan is worsening.
Just one week ago the Taliban announced its "spring offensive", with fighting intensifying around the northern city of Kunduz.
Kabul has been relatively quiet.
Fighters have been making gains in the southern Helmand province, straining Afghan military resources.
Speaking in Luxembourg, European Union Foreign policy Chief Federica Mogherini says the incident underlines the importance of working to achieve peace and stability in the region.
"In a day when we have seen an attack in Kabul that shows us how fragile the situation on the security level is in the country and that reminds us even more on the need to continue to work with a lot of energy and attention in partnership with the Afghan leadership to stabilise the country not only to provide security but also economic development and reinforcement of the institutions in the country."
