BRUSSELS - An intact German World War I submarine containing the bodies of 23 people has been found off the coast of Belgium, authorities said on Tuesday.

Western Flanders Governor Carl Decaluwe said that the find on the floor of the North Sea "is very unique".

"It's quite amazing that we found something like this," Decaluwe said. "The impact damage was at the front, but the submarine remains closed and there are 23 people still onboard."

The submarine would have had 22 crew and a commander on board, Decaluwe said.

The UB II-type dive boat that was found is 27 meters long and 6 meters wide, and is lying at about a 45 degree angle, between 25-30 meters below the surface.

From the damage to the front of the vessel, it appears that the sub may have struck a mine with its upper deck. Two torpedo tubes have been destroyed but the lower tube is intact and closed.

Video images show the submarine encrusted with barnacles and seaweed. It is also adorned with fishing gear, including nets.

Decaluwe said the U-boat was found by researchers. He declined to provide details about its location until the site has been protected. He has contacted the German ambassador because "we need to see what we can do" with the remains.

The first indications of the vessel came in 2015 when a sonar ship found signs of a large wreck off Ostend in 2015.

Thomas Termote, a diver and expert in marine archaeology, who lives in the town, carried out further investigations on his own initiative.

"We thought that all the big wrecks had already been discovered so this was a total surprise," he said.

A further dive is planned soon to clean some of the outside and check its identification number.

German authorities could then check it against their record and contact the families of the deceased.

But Termote said the wreck would be "nearly impossible" to refloat and would therefore be "considered a sea grave for the sailors".

Around 18 U-boats were stationed with the Flanders Flotilla in Bruges between 1915 and 1918. Thirteen of them were destroyed.

It's the 11th such wreck to be found in Belgian waters.

Ap - Afp