Afghan Interior Ministry announced on Wednesday the death toll from Tuesday’s major attack in Kabul has reached 64 and the number of wounded has climbed to 347.
A huge explosion has taken place in Kabul close to the US embassy and several Afghan government ministries and security agencies on Tuesday.
President Ashraf Ghani condemned the attack "in the strongest possible terms" in a statement from the presidential palace, only a few hundred metres away from the scene of the blast.
With nerves on edge in Kabul, a second explosion hit the city in the evening but no serious casualties were reported from the blast, which was caused by an improvised device, according to Interior Minister spokesman Sediq Sediqqi.
Fighting has raged around the symbolically important northern city of Kunduz in the week since the Taliban announced their annual spring offensive, although the capital has been relatively quiet since the April 12 announcement.
Kunduz, Afghanistan's fifth-largest city, fell briefly to the Taliban last September in the biggest blow to Ghani's government since NATO-led forces ended their combat operations at the end of 2014.
Gunfire rang out for more than 30 minutes after the morning blast, according to Reuters witnesses at the scene. Pictures showed windows blown out at the front of an office that houses a National Directorate of Security (NDS) unit.
The Taliban said on their Pashto-language website that they had carried out the suicide bombing on "Department 10," an NDS unit which is responsible for protecting government ministers and VIPs.
They said a suicide car bomber blew up the main gate at the front of the office, allowing other fighters, including more suicide bombers, to enter the heavily guarded compound.
A separate statement by Taliban spokesman Zabihullah Mujahid said attackers were engaged in a gun battle with Afghan security forces inside the building.
The Taliban-led insurgency has gained strength since the withdrawal of most international combat troops, and the Taliban are stronger than at any point since they were driven from power by US-backed forces in 2001.
A thick plume of black smoke had been seen rising from the area near the sprawling US embassy complex in the centre of Kabul immediately after the blast.
Warning sirens blared out for some minutes from the embassy compound, which is also close to the headquarters of the NATO-led Resolute Support mission.
The US embassy and the NATO mission both said they were not affected by the blast.