Suicide bombers have stormed a Shi'ite cultural centre and news agency in the Afghan capital, killing more than 40 people and wounding scores, many of them students attending a conference.
Islamic State said in an online statement that it was responsible for the attack, the latest in a series the movement has claimed on Shi'ite targets in Kabul.
Waheed Majrooh, a spokesman for the ministry of public health, said 41 people, including four women and two children, had been killed and 84 wounded, most suffering from burns.
The attack occurred during a morning panel discussion on the anniversary of the Soviet invasion of Sunni-majority Afghanistan at the Tabian Social and Cultural Centre, witnesses said.
The floors of the centre, at the basement level, were covered in blood as wailing survivors and relatives picked through the debris, while windows of the news agency, on the second floor, were all shattered.
"We were shocked and didn't feel the explosion at first but we saw smoke coming up from below," said Ali Reza Ahmadi, a journalist at the agency who was sitting in his office above the centre when the attack took place.
"Survivors were coming out. I saw one boy with cuts to his feet and others with burns all over their faces. About 10 minutes after the first explosion, there was another one outside on the street and then another one."
Prior to Thursday's attack, there had been at least 12 attacks on Shi'ite targets since the start of 2016, in which almost 700 people were killed or wounded, according to United Nations figures. Before that, there had only been one major attack, in 2011.
Meanwhile, a roadside bomb exploded in Afghanistan's northern province of Balkh early Thursday, killing six children.
The children, all under the age of 10, were watching a herd of animals when one child stepped on the improvised explosive device that killed all six, an official said.
Thousands of improvised explosive devices are laid by the Taliban throughout Afghanistan to hamper the efforts of Afghan security forces and stop their movements.