AS lost cities go, the flints, arrowheads and rough hewn tools do not look much - but archaeologists believe they are the first proof of a "prehistoric Atlantis" submerged off the North-East coast.

Divers have uncovered two ancient settlements under the sea off the coast of Tynemouth, near Newcastle.

One dates back to the late Mesolithic period, about 8,000 years ago.

The other, found further out to sea at the end of a long, rocky outcrop which would once have been a cliff face, is thought to be even older - possibly as old as 10,000 years.

Both settlements would once have been on dry land but have been gradually submerged as the sea rose at the end of the Ice Age.

The site, which was discovered accidentally by a team from Newcastle University, has experts in a spin because it is only the second such Mesolithic settlement to be discovered in the UK.

Last night, David Miles, chief archaeologist at English Heritage, hailed the discovery as "tremendously exciting".

He said: "We know there is a prehistoric Atlantic beneath the North Sea, where once an area equal to the size of present day Britain attached us to the continent and where prehistoric people and animals roamed."

The new site gives archaeologists a unique glimpse into this lost world.

Similar sites uncovered in the Danish North Sea have yielded a rich seam of artefacts.

Among the discoveries were preserved canoes, decorated paddles and even the remains of entire houses. They were all preserved due to the air-tight conditions deep beneath the sea.

Dr Penny Spikins, who is leading the international research team behind the submerged prehistoric landscapes project, said: "I was learning to scuba dive and was in the middle of a training session in the sea, when I noticed a lot of pieces of flint beneath me, on the sea bed.

"I was stunned by what I saw because we weren't looking for anything in particular."

She added: "The discovery of these two sites opens up a whole new underwater landscape and a new plan for us to research.

"It tells us there could have been some sort of settlement here. We originally thought that we would find submerged sites in more remote places such as the isles of Scotland.

"We think that Tynemouth could have been an important place for the early settlers because as well as having the luxury of coastal resources, they had the River Tyne nearby."

Mesolithic people were hunter-gatherers and lived in the Middle Stone Age, the era between the end of the last Ice Age 10,000 years ago, until the start of the agricultural revolution 5,000 years ago.

Dr Spikins said: "We cannot believe that this is a unique site.

"We will be fully investigating it and using the knowledge we gain in the process to try to find other sites nearby."

The team is seeking funding to continue the investigation in Tyneside.

Similar submerged Meso-lithic sites in the Danish North Sea have yielded artefacts made up of wood, bone and leather, ranging from preserved canoes and decorated paddles to house structures.