Polish authorities voiced grave concerns Wednesday after slogans praising Russian President Vladimir Putin and his war against Ukraine appeared at Polish farmers’ protests.

The Foreign Ministry said it believed that extreme groups were trying to take over the farmers’ protest movement “perhaps under the influence of Russian agents.”

On Tuesday, one tractor at a protest in the southern region of Silesia carried a Soviet flag and a banner that said: "“Putin, put things in order with Ukraine, Brussels, and our rulers.”

Interior Minister Marcin Kierwinski called the banner “scandalous,” and said that it was immediately secured by police, and that prosecutors were also investigating.