A statue of the 18th-century queen Maria Theresa in Vienna has been covered with a huge burka. The Muslim veil was placed over the statue, one of the city’s most famous monuments, by a far-right group in protest against "the Islamization of Austria."

The Identitarian youth movement chose to cover the statue of Maria Theresa, one of the country's most respected historical figures, in a large public square in central Vienna, not far from the parliament building.

A sign reading "Islamization? No thanks!" was placed by the statue.

During her 40-year reign in the 18th century, the female monarch was a devout Catholic, intolerant of other religions. The anniversary of her death was marked this week.

"We are fighting for the legacy of Maria Theresa, for the preservation of our traditions and for the freedom of our women," the group said in a statement posted on its Facebook page.

Having brought special equipment to reach the head of the huge statue, activists said they were working "day and night" to warn of the "threat of Islamization" in Europe.

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They later said the public welcomed their "important, intelligent and reasonable action," which did not cause the people of Vienna any problems such as property damage or traffic jams.

It is unclear how long the statue remained veiled. Police said they were investigating the incident, the Local reported.