Protesting farmers clashed with police in Poland’s capital Warsaw on Wednesday amid the ongoing row with Ukraine over the grain trade. 

The farmers and their supporters gathered outside the prime minister’s office and marched towards the parliament building, where they were met by riot police.

The protesters threw rocks and firecrackers at the officers, who responded with pepper spray, tear gas and stun grenades. Sporadic fights broke out, with police using batons to push back the angry farmers.

Interior Minister Marcin Kierwinski said that 23 “provocateurs” have been detained on Wednesday. A total of 13 officers were injured, including an officer who suffered a “serious” head trauma, Warsaw Police wrote on X (formerly Twitter).

Around 30,000 people took part in the protest, according to city hall spokeswoman Monika Beuth. Inspector Robert Szumiata said that although the protest was initially “overwhelmingly peaceful,” there were “groups of people who only sought to confront the police.”