More than 100 firefighters and other emergency services were called to the site of a major hotel complex in the centre of the German capital Berlin on Friday morning.

Shortly before 6.00 a.m. (local time) the 16-meter-high aquarium that stood in the lobby of the Radisson Blu Hotel ruptured, sending one million liters of seawater it contained flooding through the foyer and out onto the street.

Two people needed medical attention after suffering injuries from flying glass. All the 1,500 or so tropical fish the aquarium housed are understood to have died.

Berlin's fire service told local broadcaster RBB that workers were cleaning up water damage and smashed furniture.

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"Due to the high water pressure in the aquarium, when it burst, it took a whole lot of objects with it, which are now scattered on the street," said a spokesperson.

It was a rude awakening for around 400 guests staying in the hotel, who have been moved to other premises in the city. Sniffer dogs were also brought in to ensure that no one had been trapped in the devastation.

The usually busy Karl-Liebknecht Strasse was closed off to traffic on Friday as the cleanup got underway, and investigators tried to work out what had caused the aquarium to break. Police have told the media that they don't believe this resulted from any criminal act.

Temperatures have dropped to ferociously cold levels in Berlin in recent days. At the time of the incident, the outside temperature was around -7 degrees Celsius. Investigators will be looking to see if this played a role in the shattering of the aquarium glass.

Eyewitnesses at the scene painted a grim picture. "Everything is destroyed inside," said hotel guests Karin Wicki and Sandra Hoffmann. "There are dead fish. All the furniture is destroyed. The windows are destroyed. Shards everywhere."

The AquaDom aquarium was a popular attraction with tourists to Berlin. Its website called it "the world's largest freestanding cylindrical aquarium."

The tank contained a clear-walled elevator, which visitors used to reach the Berlin Sea Life Center.