The British Divers Marine Life Rescue organisation (BDMLR) said 10 boats formed a barrier to try to herd the deep-diving mammals from Loch Long and neighbouring Gare Loch out to sea.

But the animals changed direction and returned to the area.

The Faslane naval base, which is home to Britain's fleet of nuclear-powered submarines, is situated on Gare Loch, north of the western city of Glasgow,

Thousands of armed forces personnel from the UK, NATO and other international units are due to take part in the Joint Warrior military exercise in the area from October 4-15.

Julia Cable, a spokeswoman for the BDMLR, said: "We tried, but if the whales won't be driven out to sea there is little more that we can do.

"There are currently three whales in the loch. We have a ship that is monitoring their movements but we are not going out today (Friday)."

Joint Warrior involves "anti-submarine exercises conducted by warships, submarines and aircraft" in and around the west coast of Scotland, according to the Ministry of Defence.

But there has been concern the whales, which are sensitive to underwater sound, could be affected by the simulations.

Northern bottlenose whales are normally found off the edge of the continental shelf to the west of the UK and Ireland but it is unusual for them to be seen in coastal waters.

"We are not used to dealing with these whales but something happened out at sea that has affected the whales and drawn them into this intricate loch and island system," said Cable.

"Now they are in a territory they wouldn't normally be in. This is hard on the team and hard on the locals. We all want what is best for the wales."