Concerns are growing for an 80-year-old fisherman who went missing during a Sutherland fishing trip.
Ian McMullen from Hertfordshire was last seen on the River Oykel shortly before 5pm on Thursday.
It is understood that he had been fishing on the lower Oykel below the bridge but when he failed to return the alarm was raised around 7pm.
Police immediately launched a major search and called in assistance from the Coastguard helicopter, fire service and ambulance.
Mr McMullen is about 5ft 9in and is of large build with a distinctive brown mark on his left check.
He was wearing grey full-length waders and possibly a grey life jacket.
The Coastguard helicopter out of Inverness was deployed and continued searching until the light faded while police and other units continued looking through the night.
Among those involved in the search when it started again in the morning were police dog and fire service water units, and Search & Rescue Dog Association Scotland.
The Sutherland Inshore Lifeboat joined Assynt Mountain Rescue Team, and received ground support from the Coastguard while the Police Scotland helicopter took over in the air.
Inspector Jamie Wilson said: “As times passes we are naturally increasingly concerned for Mr McMullen’s safety.
“Extensive search activity is ongoing on the river in the area where he was last seen on Thursday afternoon and downstream.
“I would ask anyone who has information on his whereabouts or believes they have seen him to contact Police Scotland on 101 as soon as you can.”
Inspector Wilson added: “Unfortunately Mr McMullen remains missing following extensive search activity on the River Oykel and the surrounding area.
The inspector promised that “further activity will continue over the weekend.”
“I would like to take the opportunity to thank the public and all our partner agencies for their support with this search.”