A poster belonging to National Action, an online faction which advocates racial segregation, was placed on La Pasionaria, a memorial in Glasgow to British workers who volunteered for the Republican army from 1936-39.
A number of other pro-fascist posters appeared over the weekend along Clyde Street, where the memorial stands, and Glasgow Green.
Anti-fascist campaigners said they removed or obscured around a dozen images which featured swastikas and racist slogans.
Several National Action members have links to the Scottish Defence League and other far-right groups.
“It would be a mistake to attach too much significance to the actions of National Action,” wrote one anti-fascist activist in a blog posted on the A Thousand Flowers website.
“A fractured network of keyboard activists who scurry about putting stickers on lamp posts is not the sign of a strong far-right. But given the events of the last few days and the normalising of racist rhetoric around immigration it would be equally wrong to get too complacent.”
La Pasionaria, or the passionate flower, is a depiction of Dolores Ibárruri, heroine of the Spanish Republican movement.
The bronze figure was sculpted by Liverpool-based artist Arthur Dooley and unveiled in 1977.
More than 2,000 Britons volunteered to join the fight against Franco’s armies in the late 1930s. Of the 134 Scots who died, 65 were from Glasgow.
Glasgow MSP Patrick Harvie, co-convener of the Scottish Greens, said the timing of the incident was significant.
“It’s a disturbing example of the far-right and racist tendencies which have been pandered to by some of the UK’s print media, by UKIP, and by the official Leave campaign itself,” he said.
“Their irresponsible actions risk strengthening the fascist movement in the UK which has also been building in many European countries.
“It is vital that Police Scotland as well as national and local government work together to tackle this threat and keep people safe. It’s also urgent that progressive parties offer a compelling politics of the common good, which connects with people who have been let down by the mainstream and manipulated by racist and divisive parties.”
A spokeswoman for Police Scotland confirmed the force had received a report regarding the offensive content of leaflets/stickers being displayed at locations in and around Glasgow City Centre.
“Officers are conducting enquiries and will be speaking to people who have reported seeing these posters as part of their ongoing investigation with a view to identifying when and where these posters were displayed and who was responsible,” they added.