A suicide attack targeting a military academy in the Afghan capital killed at least five people early Tuesday, the first major assault in the city in months.
No group immediately claimed responsibility for the dawn attack, which comes after nearly three months of relative calm in Kabul.
The ministry of defence said five people were killed and at least six injured in the attack.
The interior ministry, however, said six people died - two civilians and four military personnel, after the suicide bomber detonated the device at around 7:00 am (local time).
Twelve others were wounded, spokesman Nasrat Rahimi said in a statement. The blast happened near the Marshal Fahim military academy, where the country's security officers are trained.
"It was a big explosion that rocked our house. We also heard gunfire afterwards. Ambulances rushed to the area quickly," resident Samiullah, who like many Afghans goes by one name, told AFP.
A security source speaking on the condition of anonymity told AFP that the attacker was on foot when he targeted a vehicle near a checkpoint as it was entering the academy.
President Ashraf Ghani slammed the attack, calling the bombing "a crime against humanity" while repeating his call for a nationwide ceasefire.
"The great nation of Afghanistan wants an end to violence, a ceasefire and a lasting peace," he said in a statement.
Taliban spokesman Zabihullah Mujahid said he was unaware of any claim for the bombing, adding that the insurgents were "investigating" the incident. The Islamic State group are also active in Kabul.
In recent weeks the Taliban have refrained from attacking major urban centres in an effort to keep talks with the US on track, but violence in the provinces has continued.
The last major attack in Kabul was in November, when at least 12 people were killed after a minivan packed with explosives rammed into a vehicle carrying foreigners during morning rush hour.
Four foreign nationals were among those wounded in the attack.
The military academy has been the scene of several attacks in the past, including one claimed by the Islamic State group last May.
Tuesday's blast comes as Washington and the Taliban wrangle over a possible deal that would see US troops begin to leave Afghanistan in return for security guarantees.
There appears to have been little progress in reaching a deal in recent weeks, however, prompting the insurgents to saddle blame on the White House and what they say are a growing list of demands.
The US and Taliban had been negotiating for a year and were on the brink of an announcement in September 2019 when President Donald Trump abruptly declared the process "dead", citing ongoing violence.
Talks were restarted in December in Qatar, but paused again following an attack near the US-run Bagram military base in Afghanistan.
As talks have fluctuated, violent attacks in the country have raged, with the number of clashes jumping to record levels in the last quarter of 2019, according to a recent US government watchdog report.