A rescue operation is taking place after a tug with two people on board capsized off Greenock in western Scotland.
The Helensburgh RNLI lifeboat, several police launch boats and watercraft rescue craft in the area went to the scene on the River Clyde when the alarm was raised around 3.30pm on Friday.
A rescue helicopter and other coast guard personnel were also at the scene.
They said there were two people on board the vessel when it capsized.
Police cordoned off the area near Custom House Quay in the town of Inverclyde.
Eyewitnesses said they saw the tug escorting the cruise ship Hebridean Princess into port when it was apparently stopped.
Daniel McBride said the tug capsized “quite instantly”.
The eyewitness told the BBC: “At that point I contacted the coastguard and was asked to keep an eye out, so I parked and watched.
“Within 12 minutes the first coastguard vessel arrived. At that point, the boat was still capsized with a visible hull in the water.
“I witnessed them banging on the hull, I guess trying to see if there was any sign in there. Unfortunately, the boat sank shortly afterwards.”
A coastguard spokesman said: “HM Coastguard is currently responding to reports of a ship capsized at Custom House Quay in Greenock on 24 February.
“Shortly before 3.30pm, Helensburgh and Greenock Coastguard Rescue Teams, a Helensburgh Lifeboat and the Prestwick Coastguard Helicopter were dispatched to assist and are searching the area.
“Scotland Police are also present.”
The Beacon Arts Center in Greenock announced on Twitter that roads around the venue have been closed by police as a result of the rescue operation and Friday night performances have been postponed.
It read: “Due to an ongoing emergency incident on the River Clyde, roads around Beacon have been closed by police and there is no access to our building.
“We have been advised by the police to cancel tonight’s performances at very short notice.”
The center added, “We will reschedule tonight’s performances or provide a full refund and contact our customers with more details as soon as possible. We appreciate your patience.”