The Turkish government intentionally incited riots earlier this year by planting members of its security services among crowds of migrants along the Greek border, German newspaper Bild reported on Friday citing a report by the German Federal Intelligence Service (BND).

Turkish officers intermingled with migrants along the border and posed as migrants themselves, throwing rocks and other objects at Greek forces in an effort to incite riots, the BND report said.

Thousands of migrants gathered on Turkey’s land border with Greece after the Turkish government announced it was opening its land and sea borders to Europe in late February.

Clashes broke out at the border between Greek police and migrants as Greece stepped up measures, deploying riot police and border guards to repel people trying to enter the country from the sea or by land.

Greece recorded over 50,000 attempts by migrants to illegally cross the border by mid-March, as Ankara and Athens accused each other of using migrants and refugees for their own political ends.

Turkish authorities have denied the claims, Bild said, while the BND failed to disclose further details on the allegations to the daily when asked to comment.