The first Arabic-language street sign to have been erected in the German city of Düsseldorf has been vandalized with supporters of a right-wing identitarian group claiming responsibility.

The sign, which had recently been praised by local Islamic associations and the Green Party as a symbol of diversity, was covered up by stickers renaming it Karl-Martell-Straße, a nod to the Frankish leader often portrayed as the savior of Christian Europe from a full-scale Islamic invasion by the Umayyad Caliphate back in the eighth century.

A sticker depicting a horsed knight driving people away with a lance was also used to cover up the Arabic-language sign.

Revolte Rheinland, a right-wing group has claimed responsibility for the vandalism. In a social media post on Telegram, they wrote: “So that this distortion of history and gesture of submission does not go unanswered, activists not only covered the sign of shame last night, but also renamed the entire street after a great European who, almost 1,300 years ago stopped the Islamic land grab.”

In addition to the stickers, the activist group attached a poster to the street sign which read: “Remigration over submission.”

After its praise for Charles Martel, the group wrote: “But unlike then, this time there is no need for an armed invasion. Our politicians have willingly given up our cities. This street sign is symbolic of this process of submission, which is why we renamed it after a great European who we need more than ever today. Then the lance, today the deportation aircraft.”

Düsseldorf police announced on Monday an investigation had been opened into the incident which has now been taken over by state police.

Ten more multilingual street signs are planned across German cities as the country embraces the diversity it its immigration policies have created. A recent study by the Pew Research institute predicts the Muslim population in Europe will triple over the next 30 years, rising up to 75 million if the continent continues its demographic trends.