A gunman killed himself Tuesday after shooting dead six patients at a hospital in the eastern Czech city of Ostrava, in what the premier has called "an immense tragedy".

The attacker gunned down people at close range at the trauma ward of the Faculty Hospital in Ostrava, a steel hub located some 300 kilometres (190 miles) east of Prague.

Four men and two women died during the assault, which police said lasted only a few seconds.

Two other people were seriously wounded -- one is in a critical condition after being shot in the head and the other is past the worst following surgery, rescue services said. A third person sustained light injuries.

The gunman had chased children out of the waiting room before opening fire, according to the DNES broadsheet daily.

Police said they had not yet determined what drove the 42-year-old to launch the attack but reports suggested he was mentally unstable.

"I was told the dead victims were people sitting in the waiting room of the trauma ward. Fortunately, there were not as many as usual," Prime Minister Andrej Babis told local media in the immediate aftermath of the shooting.

"The gunman was allegedly shooting from a close range, aiming at the head and neck."

The shooter then fled the scene in a silver Renault Laguna car, sparking a police hunt involving hundreds of officers and two helicopters.

"His mother cooperated with the police -- he came home, told her he had shot people and that he was going to shoot himself now," Babis said at the site of the crime after travelling to Ostrava.

The man had turned the gun on himself inside the vehicle as police were about to capture him in a village just northwest of Ostrava, regional police chief Tomas Kuzel said. "We identified the gunman using hospital cameras. We deployed two helicopters, identified his car... and when one helicopter descended over the car, he shot himself in the head," Kuzel told reporters.

Interior Minister Jan Hamacek said the man died despite resuscitation efforts.

Police said the gunman had used the Czech-made nine-millimetre semi-automatic CZ 75 pistol in the attack, which took place shortly after 0600 GMT.