Dutch police have arrested a gunman who killed at least three people in twin shootings in the city of Rotterdam.

They say the male attacker, 32, opened fire in a home before setting it alight, then stormed the city's Erasmus Medical Center on Thursday.

He was a student at Erasmus University, which is affiliated with the hospital.

A woman, 39, and her 14-year old daughter were killed in the first shooting. A male lecturer, 43, was shot dead at the hospital.

Footage has emerged showing a man in camouflaged clothing being taken from the hospital building in handcuffs. The motives for the attack were not immediately known.

A security guard who says he was first on the scene told the BBC it was a "shocking" day.

"It was terrible, terrible," he said, visibly shaken and not wanting to give his name.

He said that the gunman had not entered the medical centre through the main entrance.

Dutch Prime Minister Mark Rutte wrote in a post on social media: "My thoughts go out to the victims of the violence, their loved ones and to all the people who have been in great fear."

t a news briefing after Thursday's shooting, Rotterdam police officers said the gunman - who has not been publicly named - was known to them. He was convicted of animal cruelty two years ago.

The police said there were no indications of a second gunman.

As the shooting started at the medical centre, employees were seen running out of the building with patients, some of them on stretchers.

Signs were seen taped to two hospital windows reading: "Room 32. We can't get out!"

Barak, a 27-year-old student from Israel, told the BBC he was in a job interview when the shooting began. When he came out, it was scary with so many sirens and messages.

"We can't believe it was a student like us," he added.

Another student told RTL Nieuws website: "First there was a shooting on the fourth floor. Four or five shots were fired. Then a Molotov cocktail was thrown into the education centre."

Elite police units - including snipers - stormed the hospital, and helicopters were seen hovering over the hospital building.

Before his arrest, the police said the dark-haired tall suspect in combat gear may have been on a motorcycle, and was carrying a backpack, headphones and a handgun. (BBC)

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