KABUL, Afghanistan (CNN) -- A military hospital in the Afghan capital of Kabul has come under attack, with at least three people killed and at least 50 others injured, according to government officials.
Sardar Mohammad Daud Khan Hospital, the biggest and best-equipped facility in the country, was targeted by attackers Wednesday morning, Afghan Interior Ministry Spokesman Sediq Sediqqi told CNN. Saleem Rasooli, the head of Kabul Hospitals, confirmed the casualties to CNN.
The injured have been taken to the Wazir Akbar Khan hospital, Smael Kawosi, media relation officer for the Ministry of Health, said.
The facility, known locally as the "400 bed" hospital, is only a few hundred meters from the US embassy and the diplomatic quarter of Kabul.
Initial reports indicate attackers detonated an explosion before entering the hospital compound, he said, adding that Afghan National Police special forces are on the scene, trying to repel the ongoing attack.
Initial reports indicate attackers detonated an explosion before entering the hospital compound, he said.
Eyewitnesses told CNN explosions were first heard around at 9 a.m. (11.30 p.m. Tuesday ET) local time.
"At first there was a firing followed by a huge blast," an employee at a nearby hospital said.
A press statement from the Afghan Defense Ministry indicated that a suicide bomber had detonated the explosive.
An employee at an Italian restaurant nearby said she heard one explosion around 9 a.m. and heard gunfire around 25 minutes later.
The statement said three other assailants, wearing medical personnel uniforms entered the hospital and made their way to the second and third floors of the building.
"So far one of the attackers has been killed and the remaining two are hiding behind a staircase," the statement says. It adds that the reason for the delay in neutralizing the attackers is that the security forces were busy evacuating the facility of patients.
"Now all the patients are in a safe place and the operation to kill the remaining attackers is underway," it said.
A Taliban spokesman, Zabiullah Mojahid, denied responsibility for the attack in a tweet, saying: "today's attack on hospital in Kabul has nothing to do with the Mujahidin of Islamic Emirate," using the group's formal name.
In the vacuum of a claim from the Taliban, the ISIS-affiliated news agency Amaq said ISIS claimed responsibility for the attack. Although the group usually attacks sectarian targets, it is credible that it planned and carried out the attack. CNN, however, is unable to independently verify the claim.
Afghan Chief Executive Abdullah Abdullah condemned the attack.
"I condemn the terrorist attacked on hospital in Kabul," he tweeted.
"While we work for peace, we'll avenge the blood of our people."
NATO forces in Afghanistan said that the organization was standing by to assist Afghan security forces, tweets from Operation Resolute Support said.
"Once again insurgents show complete disrespect for humanity by attacking a hospital. We stand with Afghan people against terrorism."
The NATO tweets condemned the attack, using an older name for the hospital.
Militants have long targeted loosely guarded targets in Kabul and across Afghanistan. Last month, at least 20 people died after a suicide blast outside Afghanistan's Supreme Court in Kabul, police and other officials told CNN.
A suicide bomber detonated his explosives in a parking lot near the court in the Afghan capital, according to Basir Mojahid, spokesman for Kabul's chief of police.
Earlier in the year, two suicide bombings near the Afghan Parliament in Kabul, an explosion at a Kandahar province government compound and a suicide bombing in Helmand province -- left dozens of people dead and wounded.
The Taliban claimed responsibility for the Kabul attacks, which killed at least 36 people and injured 76 others in the capital.
Last summer, seven students, three police officers and two security guards were killed in the attack on the American University of Afghanistan campus in the capital.
Police searched the university's grounds and killed two attackers who stormed the campus with guns and explosives, Fraidoon Obaidi, chief of Kabul police's criminal investigation department, said. The gunmen detonated explosives and fired guns, witnesses said, causing some students and faculty to flee.