Three pilot whales have become stranded on the shore of a sea loch.
Rescuers at the scene said the whales were part of a pod of around 60 which got trapped in the Kyle of Durness, one of Britain's most northerly points, in the Scottish Highlands.
The British Divers Marine Life Rescue charity said the three whales are being given first aid on the beach.
Between 15 and 20 pilot whales which were thought to be in danger of stranding have been herded back to a deeper channel of water where they rejoined the larger group.
The larger group may still become stranded once the estuary tide goes out. The Navy and Coastguard are also helping with the rescue, which is expected to continue through the night into tomorrow.
The Scottish Agricultural College said another 20 of the whales could be heading for shallow water.
SAC vet Dr Andrew Brownlow is making his way to the Kyle of Durness. He will conduct post-mortem examinations on any dead whales.
In May, around 60 pilot whales appeared in Loch Carnan, South Uist, although they left the loch after one of the mammals died. The dead whale was later found on an island in the loch. A post-mortem examination suggested it had died of infection.
Rescuers later said a second whale was found dead in the same loch. It is thought to have died elsewhere and floated in on the tide.
At the end of October last year, other pilot whales almost got stranded in Loch Carnan. Less than a week later 33 whales, believed to be the same group, were found dead on a beach in Co Donegal in Ireland.
Pilot whales are known to prefer deep water but come inshore to feed on squid, their main food.
The rescue charity said one of the beached whales is a calf.
Operations manager Stephen Marsh said: "This is a major operation, as it always can be with this species. Pilot whales are gregarious, family-orientated animals and will follow a member of their pod that may be in distress or ill.
"Kyle of Durness is not a good place for them to be, as it practically empties on the outgoing tide and is full of sandbanks - potential stranding sites for any whale.
"We're really thankful that the Navy and Coastguard have been on hand to work under our guidance until our team arrived at the scene. And they continue to be a major asset in this operation."