A bronze statue worth around £20,000 has been stolen from Kelvingrove Art Gallery and Museum in Glasgow.
A thief walked out with the 13kg statue on Sunday afternoon while the gallery was open to visitors.
Dreaming, by British pop artist Gerald Laing, was taken from the first floor of the building at around 4.30pm. A member of staff had last seen the sculpture 3.45pm.
But 45 minutes later the alarm was raised by staff carrying out routine checks when the statue was nowhere to be found.
Strathclyde Police are now examining CCTV images from a number of areas within the museum.
This is the first theft in Scotland's most popular museum since it was reopened to the public in 2006.
A spokesman for Glasgow Life said: "This was a deliberate act. Someone has stolen from the people of Glasgow– as with all of our collections, this work belongs to them. We are working with the police and other agencies and would appeal for the safe return of this work of art.
"Since reopening after refurbishment in 2006, we have welcomed more than nine million visitors to Kelvingrove and had no incidents of work being taken from public view.
"Thanks to the quick action of staff, we have been able to identify a short time frame where we believe the bronze was stolen – and are in the process of examining CCTV footage from across the museum to identify those responsible."
Laing created the work in 1979 and it was purchased with the support of the National Fund for Acquisitions for Glasgow Museums in 1981.
The prominent artist, who claimed Andy Warhol as a friend, re-built Kinkell Castle on the Black Isle in the Highlands where he lived and worked until he died last year.
The statue weighs 12.8kg and is 35.5cm by 20cm by 31.1cm. Laing died in November 2011 at the age of 75.