KABUL, March 8 (Xinhua) -- At least three persons were killed and 66 others wounded in a terrorist attack against a military hospital in Kabul on Wednesday, and three attackers also died, local media reported.

One suicide bomber struck the back gate of Sardar Mohammad Daud Khan Hospital in fortified Wazir Akbar Khan diplomatic district in the morning.

The blast enabled four terrorists armed with guns and grenades to enter the main building and opened indiscriminate fire on patients and medical staff, according to security sources.

"Three killed and 54 injured were admitted in nearby Wazir Akbar Khan hospital following the attack," Ismahil Kawosi, spokesman of Public Health Ministry, was quoted by local media Tolo News as saying, adding the number casualties was likely to change.

Another 12 wounded were shifted to Kabul Emergency Hospital, he said.

At least five terrorists were involved in the attack, one terrorist was killed by his bomb and two others were shot dead by security forces, according to initial information by security sources.

A military helicopter dropped Afghan commandos to the top of the building and sporadic clashes was still going on in the seven-story building as of midday.

"We are aware of the report of Kabul hospital attack and are monitoring the situation. We stand ready to assist Afghan security services," the NATO-led Resolute Support coalition forces twitted.

The 400-bed hospital, which is located in the diplomatic district near the U.S. embassy, is the main and largest military hospital in the country.

No group has claimed responsibility for the attack yet and Taliban militant group has denied its involvement in the deadly attack.