A gunman killed himself Tuesday after shooting dead six patients at a hospital in the eastern Czech city of Ostrava, in what the country's 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 east of Prague, police said.

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

A father was gunned down as he protected his daughter, according to Czech Television. Two men were prison service employees, said the justice ministry.

Two other people were seriously wounded. A woman was in a critical condition after being shot in the head and a man was past the worst following surgery, rescue services said. Another man sustained light injuries.

Police said they had not yet determined what drove the 42-year-old to launch the attack.

"The gunman was allegedly shooting from a close range, aiming at the head and neck," Prime Minister Andrej Babis told local media in the immediate aftermath of the shooting.

The broadsheet daily DNES quoted a witness as saying the gunman had chased children out of the waiting room before opening fire.

"He walked up to a victim, shouted 'one' and shot, then he went to another, shouted 'two' and shot," she said.

Another witness told Czech TV the gunman had tried to recharge after emptying his first cartridge but was interrupted and fled.

The shooter then left 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.

'A catastrophe'

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.

"As far as we know, the man is not in our database of legal gun owners," Kuzel said, adding there was no indication that he had an accomplice.

The man had three entries in his criminal record for violence and theft, said Kuzel. 

Czech media identified the shooter as a builder from the nearby Opava district.

His boss, named as Ales Zygula, told the public Czech Radio that the attacker had "decided he was seriously ill and that no one wanted to treat him.

"We noticed a slight change in his behaviour," he added.

A local singer who claims he knew the man said he had believed he had cancer.

Prior to his death, police had urged "maximum possible caution" as they tweeted pictures of the man who had thick black hair and was wearing a red and black jacket and trainers.

Babis described the shooting as "a catastrophe" and said sirens would sound across the country at noon next Tuesday to honour the dead.

"It's something we're not used to in our country," he added. "Nobody understands why the gunman was so merciless."

President Milos Zeman also expressed his condolences.

"I'm with you in my heart, I'm thinking of you in these tragic hours," he said in a tweet posted by his spokesman.

Gun rampages are rare in this EU member country of 10.7 million people.

In 2015, a restaurant guest in the southeastern town of Uhersky Brod shot dead seven men and a woman before committing suicide.

In March this year, a patient at a Prague hospital shot two fellow patients after an argument in a room. One of the men died.

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