A car bomb has killed at least 80 people and wounded more than 350 in Kabul, the public health ministry says.

The explosion occurred during the morning rush hour in a busy part of the Afghan capital that houses many foreign embassies and government departments.

The Australian and German embassies, the Foreign Ministry and the Presidential Palace are all in the area.

Australian diplomats in Kabul are in lockdown but all embassy staff are safe and have been accounted for, Department of Foreign Affairs and Trade secretary Frances Adamson said.

It is unclear whether German embassy staff in Kabul were injured or killed, a security source said.

"It's unclear at the moment whether German staff have been affected," the source told Reuters.

The French embassy was damaged but there were "no signs at this stage" of any French victims, a government spokesman said.

No group has immediately claimed responsibility for the blast but both the Taliban and the Islamic State group have staged large-scale attacks in the Afghan capital in the past.

Details on the blast in the in Wazir Akbar Khan district are sketchy and Najib Danish, deputy spokesman for the Interior Ministry, did not have a breakdown of casualties.

The explosion occurred at the peak of Kabul's rush hour when roads are packed with worktime commuters.

The neighbourhood is considered Kabul's safest area, with foreign embassies protected by dozens of blast walls and government offices, guarded by police and national security forces.