Searches are continuing in Papa Westray, Orkney, to trace missing Sergei Ivanov.
Mr Ivanov, 55, was last seen at around 10am on Monday, April 3 walking near to his home address on the south of the island.
He was reported missing on Sunday, April 9.
Inspector Keith Bendall said: “Coastline and land searches have been carried out and police have been assisted by the Coastguard including the use of the helicopter.
“As time goes by we are increasingly worried for Sergei’s welfare and it is out of character for him not to be in touch with family and friends.”
Inspector Bendall added: “The community has supported police and we would like to thank them for that.
“In addition we would ask people to check any sheds or outbuildings they have for signs that someone may have sought shelter there.
“The forecast is poor for today with high winds however we will continue searches where possible.”
Sergei was last seen wearing a black jumper, black trousers, long black coat (below his knees) and black work-type boots.
He is described as being around 5ft 10ins tall, with long grey hair and a medium build.
Anyone who may have information should contact the police on 101.