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 came after nearly three months of relative calm in Kabul.
The ministry of defense said five people were killed and at least six injured.
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 (0230 GMT).
Twelve others were wounded, ministry 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," Samiullah, a resident 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 called the bombing "a crime against humanity" while repeating his call for a nationwide cease-fire.
"The great nation of Afghanistan wants an end to violence, a cease-fire 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 Islamist extremist Taliban have refrained from attacking major urban centers in an effort to keep talks with the United States 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.
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 came as Washington and the Taliban wrangle over a possible deal that would see U.S. troops begin to leave Afghanistan in return for security guarantees.
There appeared to have been little progress in reaching a deal in recent weeks, however, prompting the insurgents to blame the White House and what they said were a growing list of demands.
Late Tuesday, Ghani said on Twitter that U.S. Secretary of State Mike Pompeo had called to inform him "of the notable progress made in the ongoing peace talks with the Taliban. The Secretary informed me about the Taliban's proposal with regards to bringing a significant and enduring reduction in violence."
"This is a welcoming development," Ghani said
The United States 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 unrest.
Talks were restarted in December in Qatar, but paused again following an attack near the U.S.-run Bagram military base in Afghanistan.
In his annual State of the Union address on Feb. 4, Trump renewed his vow to negotiate a troop withdrawal from Afghanistan.
"We are working to finally end America's longest war and bring our troops back home," he said, offering his blessing for the negotiations with the Taliban.