The Turkish government and a far-right Dutch politician are in a row over a tweet portraying the Turkish president as a terrorist and Islamic State (IS) supporter.

On Monday, Dutch lawmaker Geert Wilders tweeted a picture of Turkish President Recep Tayyip Erdogan’s face on a Turkish flag and the IS flag. “Terrorist,” he wrote in the tweet.

Wilders is the leader of the Party for Freedom and a member of the Dutch House of Representatives. He is known for his criticism of Islam. He has called for the Islamic holy book the Quran to be banned in the Netherlands and regularly speaks out against Muslim immigration and the “Islamization” of the country. Wilders is regularly accused of bigotry against Muslims for his views. He has been under round-the-clock police protection since 2004 due to threats.

Turkish prosecutors filed an investigation into Wilders for the tweet, alleging that it constituted an “insult.” Many Turkish politicians were angered by the tweet. Vice President Fuat Oktay called Wilders “Europe’s spoiled child.” Omer Celik, the spokesman for Erdogan’s Justice and Development Party, said Wilders is a “fascist,” the state-run Anadolu Agency reported Tuesday.