A loud explosion and follow-up gunfire were heard near the Afghan communication ministry in Kabul on Saturday, officials said.
The blast occurred a day after talks collapsed between the Taliban and Afghan representatives, but no one claimed immediate responsibility. At least six people have been wounded, according to the health ministry.
Police chief General Sayed Mohammad Roshandil said that the bomber blew himself up outside the telecommunications ministry, clearing the way for the other attackers to enter the building and the heavily-guarded government compound in central Kabul.
“The information that we have is four attackers have placed themselves near the communication ministry and are engaged in gun battles with the Afghan security forces,” Amanduddin Shariati, a security official in Kabul said earlier.
Security forces were engaged in an operation against the attackers inside the building, Roshandil said. The ministry has 2,000 employees, the Tolo News twitter account quoted him saying.
The Ministry of Communication and IT is located in downtown Kabul, about two kilometers (1.25 miles) from the green zone, close to the heavily-fortified Serena Hotel, one of the very few Kabul hotels still used by foreign visitors.
Interior ministry spokesman Nasrat Rahimi said an explosion was heard near the communication ministry around 0710 GMT (11:40 am), followed by sporadic gunfire.
Local television footage showed a small plume of smoke near the ministry, and people climbing out the windows on a lower level.
Intermittent firing could still be heard more than 30 minutes after the blast, and the area had been cordoned off by security forces.
One security official, who declined to be identified by name, said the initial blast appeared to have been caused by a suicide bomb at the entry to the ministry.
A witness quoted by the Tolo News said attackers appeared to be fighting security forces on the first floor of the ministry headquarters.
There was no confirmation from the Afghan police.
Spring offensive, failed talks
The explosion comes the week after the Taliban announced their annual spring offensive and amid ongoing fighting across Afghanistan.
The Afghan branch of the Daesh group has also previously carried out multiple deadly attacks in Kabul.
The capital has in recent weeks enjoyed a period of relative calm, after a horrific year last year in which it saw a string of attacks including a massive bomb that was concealed in an ambulance and killed more than 100 people.
This week in the Qatari capital Doha, a summit planned between the Taliban and officials from across Afghanistan fell apart at the last minute due to bickering over who should attend the conference.
The collapse comes at a critical time and amid continued bloodshed in Afghanistan, where the Taliban now control or influence about half of Afghanistan and 3,804 civilians were killed there last year, according to a UN tally.
Taliban officials are separately negotiating with the United States, which wants to forge a peace deal with the militants.