(CNN)At least 20 people were killed and 30 wounded in blasts at Afghanistan's biggest military hospital on Tuesday, according to officials.
Gunfire followed the explosions at the entrance of Kabul's Daoud Khan Military hospital, a 400-bed teaching facility near the capital's former diplomatic quarter. IS Khorasan (ISIS-K), an ISIS affiliate that operates in central Asia, claimed responsibility for the attack.
In a statement posted on Telegram, ISIS' news agency, Amaq News,claimed that five of ISIS-K fighters were involved in the attack. One of the fighters detonated a suicide belt amidst a gathering of Taliban fighters at the hospital's external gate, the statement said.
The Telegram post said the other fighters stormed the building and shot at Taliban members.
A doctor treating incoming patients at the nearby Wazir Akbar Khan civilian hospital said at least 15 wounded people had been admitted to his facility's emergency ward, several in critical condition. In addition, the Italian humanitarian NGO "Emergency" tweeted that nine injured were brought to its hospital in Kabul.
Three armed men were seen inside the compound of the hospital near the entrance of the building after two blasts rocked the area, according to footage posted on Facebook and obtained by CNN.
The video was filmed from inside the hospital by a man who wrote on Facebook he was "trapped" inside a room and in hiding. In the video, a fourth man appears laying on the floor.
Photographs shared by residents showed a plume of smoke over the area of the blasts and witnesses said at least two helicopters were flying over the area, Reuters reported.
A health worker at the hospital, who managed to escape, told Reuters he heard a large explosion followed by a couple of minutes of gunfire. About ten minutes later, there was a second, larger explosion, he said. He said it was unclear whether the blasts and the gunfire were inside the sprawling hospital complex.
There was no immediate claim of responsibility. But the official Bakhtar news agency quoted witnesses saying a number of fighters from the Afghan affiliate of ISIS entered the hospital and clashed with security forces, Reuters reported.
The Daoud Khan Military hospital has been targeted before. In 2011, suicide bombers linked to the Taliban blew themselves up inside the facility, killing six people and injuring 26 others
In 2017, ISIS-K, as the affiliate is known, mounted a complex attack on the hospital, killing more than 30 people. The group has carried out a series of attacks on mosques and other targets since the Taliban's seizure of Kabul.
Afghanistan has been embroiled in crisis since the hardline Islamist Taliban movement drove out the Western-backed government in August. Billions of dollars in assistance were halted and the international community has warned that the country would soon collapse into chaos.
Last Friday, three guests were shot dead at a wedding reception in eastern Afghanistan, apparently because music was being played.