At least 40 people were martyred and 30 wounded in a bomb attack on the Afghan Voice news agency in the capital, Kabul, on Thursday, an Interior Ministry spokesman said.
There was no immediate claim of responsibility for the latest in a series of attacks on Afghan media groups but the Taliban issued a statement denying any involvement.
Photographs sent by witnesses showed what appeared to be serious damage at the site and a number of dead and wounded on the ground.
Najib Danish, spokesman for the Interior Ministry, called it a suicide attack and confirmed there were casualties.
A health ministry official said there were heavy casualties among students attending a panel discussion with researchers at the agency's offices.
The attack, the latest in a series to hit Afghan media groups in recent years, follows an attack on a private television station in Kabul last month.
According to a report this month by media freedom group Reporters without Borders, Afghanistan is among the world's most dangerous countries for media workers with two journalists and five media assistants killed doing their jobs in 2017.
Separately, Dawlat Abad District Gov. Mohammad Karim said a powerful mine killed six shepherd children ranging in age from 8 to 10 on Wednesday.
No one immediately took responsibility for the attack but Karim blamed the Taliban, saying the insurgents planted the mine to target Afghan officials and security forces.
Afghanistan has the highest number of mine victims in the world, which along with other roadside bombs, martyred or wound an estimated 140 people every month.
Elsewhere, a Taliban attack on a security police post in central Ghazni province Wednesday night left three police dead and one other wounded, said Mohammad Zaman, provincial chief of police.
Source: News Agencies, Edited by website team