Almost 140 sightings of missing teenager Liam Smith have been dismissed by police.

Searches are being carried out near Crathes in Aberdeenshire where the 16-year-old is thought to have got off a bus from Aberdeen 11 days ago.

Liam was last seen on CCTV at Union Square shopping centre in Aberdeen shortly before boarding the bus, which was heading towards Banchory.

Officers have received 139 sightings of Liam from the public in various locations across the north east including Inverurie, Kemnay and Rothienorman.

However, each of these sightings have been eliminated and police are now re-appealing for help to find the missing boy.

Chief inspector Martin Mackay said: "Every available police resource has been dedicated to our search for Liam and it continues to cause us all great concern that he has not yet been found.

"11 days is a long time for a teenage boy who has little experience of the outdoors to be missing and as more time passes without seeing or hearing from him, we need to be realistic about the options we have moving forward.

"The terrain we are entering with regard to our searches is extremely challenging - not helped by the current weather - and even our own officers are finding it difficult to navigate certain areas.

"They are trained and experienced to do this though and we will continue to ensure that all the land we need to cover is searched effectively."

Liam is white, slim and 6ft 4in. He has short brown hair and walks with a distinctive gait.

When last seen he was carrying a camouflage North Face rucksack and was wearing Nike Air Max trainers.

He bought Lucozade, Jaffa Cakes and a Dairy Milk at Sainsbury's before he left Aberdeen.

Mr Mackay said the force had received multiple offers of assistance from concerned locals but due to the risks of injury caused by perilous terrain the offers had been turned down.

"I must stress just how challenging the land is we are dealing with ranging from dense wooded areas to expanses of water, and we don't want anyone put in harm's way," he said.

"Organised public searches can also be very resource and time-intensive to coordinate and our time is extremely precious at the moment.

"There are still ways you can help us though. Firstly I know that people will be out walking in the Crathes Estate area anyway, whether it's to walk your dog or cycle, and I welcome anyone's efforts to keep an eye out for anything that could help us locate Liam.

"I also continue to urge anyone with information that could help us establish why Liam would head in the Deeside direction, or if he has mentioned places of interest to you in the past, to let us know.

"Finally I would ask to the public to continue supporting our efforts, which have so far included sharing our social media posts to printing off posters. The response to our appeals has been unprecedented and it has not gone unnoticed by Liam's family nor us."

Anyone with information can contact 101.