Police have urged members of the public to be vigilant as searches for a man missing since before Christmas ramp up.

Officers as well as volunteers from Wiltshire Search and Rescue (WILSAR) have spent much of Saturday scouring Coate Water as part of the search for missing man Brian Roberts.

They were joined by colleagues from Lowland Rescue Oxfordshire and described the callout as one to look for a "high risk missing person".

Swindon Advertiser: Brian Roberts has been missing since December 23Brian Roberts has been missing since December 23 (Image: Wiltshire Police)

Volunteers took to an inshore boat to search the lake and banks.

Meanwhile, searches were also taking place "in a number locations throughout the town and further afield".

Brian, 59, has not been seen since December 23, and his last contact with anyone was on January 3.

LIVE UPDATES: Volunteers search Coate Water for missing Brian Roberts

READ MORE: Police growing 'increasingly concerned' for welfare of Brian Roberts

Wiltshire Police said in a renewed appeal on Friday that they were "increasingly concerned for his welfare".

Now, in a statement on Saturday afternoon, the force have urged Swindon residents to "be vigilant".

They are not asking any members of the public to join the searches.

A spokesperson for Wiltshire Police told the Adver: "We appreciate that members of the public will want to help - at this stage, we are asking for them to be vigilant and to keep an eye out for anyone who matches the images we have issued and call us as a matter of urgency should they have any information that could help our search.

"We are not asking for any further volunteers to help take part in searches as WILSAR are providing that level of support."

Earlier in the week, police released CCTV footage of Brian's last known location.

In a statement aimed directly to Brian, police said: "We would like to directly appeal to Brian – if you are reading this, please let us know you are safe.

Swindon Advertiser: CCTV footage is the last time Brian was seen. He is believed to be wearing these clothesCCTV footage is the last time Brian was seen. He is believed to be wearing these clothes (Image: Wiltshire Police)

"Drop into a local police station, or make contact with a friend or family member."

Members of the public are also being asked to help if they can by reporting any information they might have that could lead to Brian being found.

"We are growing increasingly concerned about Brian’s welfare and would urge anyone with information to contact us immediately.

"We believe Brian is wearing the clothes he is pictured wearing on CCTV."

If you can help, please call 101 and quote reference number 54230001127.