An attempt to herd a pod of northern bottlenose whales back out to sea ahead of a major international military exercise is under way.
Rescuers are guiding the whales out of Loch Long amid concerns over the impact that Exercise Joint Warrior, scheduled to take place in the area, could have on them.
Experts from British Divers Marine Life Rescue (BDMLR) have monitored the pod in and around the River Clyde over the last month.
At 10.30am on Thursday, the operation to move the whales began as several small vessels encouraged the animals to move down the loch and into deep water where they can feed.
BDMLR tweeted an update at 12.20pm, which said: "The first group of boats are in position and gently moving the whales towards the mouth.
"They will form a barrier with boats in position to prevent the animals turning in the wrong direction. The shore-based teams are monitoring all movement."
A pair of whales first seen in Loch Goil were spotted at the mouth of the Clyde near Millport, on the Isle of Cumbrae, some weeks ago.
Since then, five whales have been seen in separate locations in Loch Long, with some of them entering smaller lochs nearby.
Northern bottlenose whales are a deep-diving species normally found off the edge of the continental shelf to the west of the UK and Ireland.
A spokesman for the Royal Navy at Faslane told the PA news agency that members of Queen's Harbour Master Clyde, based at HM Naval Base Clyde, had met BDMLR on Wednesday.
Several vessels from the Ministry of Defence Police's Clyde Marine Unit are involved with representatives from the QHM Clyde organisation, both on the water and in harbour control.
An MoD spokesman said: "The Royal Navy takes its environmental responsibilities very seriously and continues to work with the relevant UK authorities to ensure all practical measures required to reduce environmental risk and comply with legislation are taken.
"A necessary series of safety checks is observed and an environmental risk assessment carried out before any underwater task is undertaken by MoD in order to minimise any potential risk to marine life."