Afghan officials say Taliban militants have attacked an office of the country's main security agency in Kabul, killing at least 28 people and wounding more than 300.
Interior Ministry spokesman Sediq Sediqqi told RFE/RL that the April 19 attack began with a suicide car bomb during the morning rush hour, followed by an assault by armed militants.
The attack -- near the Defense Ministry in the capital's central first district -- targeted an office that houses a National Directorate of Security unit responsible for protecting government officials.
Kabul police chief Abdul Rahman Rahimi said most of the 28 people confirmed dead were civilians.
He said an explosives-laden truck detonated in a public parking lot next to the security-agency building.
Rahimi said at least one gunmen was killed by security forces after the explosion.
Casualties included both civilians and members of Afghan security forces.
Just hours after the first blast, a second explosion hit the city in the evening but no serious casualties were reported.
The blast was caused by an improvised device, according to Sediqqi.
The Taliban claimed responsibility for the first attack, which comes a week after the militant group announced the start of its annual spring offensive.
PHOTO GALLERY: Death, Chaos In Kabul
More Than 300 Casualties In Massive Kabul Attack
A police commander, Obaidullah Tarakhail, said the blast was "one of the most powerful explosions I have ever heard in my life."
He added that he couldn't see or hear anything for 20 minutes after the initial explosion. "All around was dark and covered with thick smoke and dust," he said.
The explosion also severely damaged dozens of apartment buildings, shops, and government buildings in the area.
The presidential palace, located about 2 kilometers from the blast, condemned the "cowardly terrorist attack," saying it "will not weaken the will and determination of Afghan security forces to fight against terrorism."
President Ashraf Ghani condemned the attack in a statement and said it was the result of the Taliban suffering losses in fighting against security forces in other parts of the country following the declaration of its annual spring offensive.
The attack "clearly shows the enemy's defeat in face-to-face battle with Afghan security forces," Ghani statement.
Sediqqi told RFE/RL that "the suicide attack by the Taliban, in which a vehicle was used, is a clear sign of [the Taliban's] failure."
He said the Islamic extremist group had recently suffered defeats in confrontations with Afghan security forces in the northern provinces of Kunduz, Takhar, Badakhshan, and Jowzjan.
"The Taliban [suffered] huge casualties in the last 24 hours and now they carry out a suicide attack in Kabul," Sediqqi said. "It is a clear sign of their defeat."
Sediqqi said several gunmen fought with security forces after the blast. Afghan officials said those gunbattles had ended.
A Taliban spokesman, Zabihullah Mujahid, however, said several of its fighters were still inside the security agency's compound and fighting.
In a statement isued on April 19, White House spokesman John Kirby said the "United States condemns in the strongest terms the attack today in Kabul."
"This incident underscores the harm the Taliban and other violent extremists continue to inflict on the Afghan people," he added.
UN Secretary-General Ban Ki-moon strongly condemned the attack and said "there is no justification whatsoever for attacking civilian people as well as security people."
Ban also urged the international community to cooperate in tackling extremism, saying, "We must fight against these terrorist attacks."
"This attack shows the devastation caused by the use of explosive devices in urban areas and once more demonstrates complete disregard for the lives of Afghan civilians," said Tadamichi Yamamoto, the secretary-general's deputy special representative for Afghanistan.
"The use of high explosives in civilian populated areas, in circumstances almost certain to cause immense suffering to civilians, may amount to war crimes," Yamamoto added.
"Today's attack shows the insurgents are unable to meet Afghan forces on the battlefield and must resort to these terrorist attacks," said General John W. Nicholson, the new commander of the NATO-led coalition in Afghanistan. "We strongly condemn the actions of Afghanistan's enemies and remain firmly committed to supporting our Afghan partners and the National Unity Government."
The Taliban began its spring offensive last week by targeting the northern city of Kunduz, which the militants briefly captured last year.
But after three days of intense fighting, Afghan officials said security forces had repelled the attack and claimed to have killed dozens of Taliban fighters.