BERLIN (AFP) - More than 20,000 Kurds protested against the Islamic State group in the western German city of Duesseldorf Saturday, according to the police.

Several Kurdish organisations called the demonstration to protest attacks by IS militants on Kurdish towns in Syria, particularly the besiegement of the city of Kobane.

Clashes between Kurds and radical Muslims in the northern German cities of Hamburg and Celle left more than 20 people injured earlier this week.

Concern has grown in Berlin about a spillover of the tensions in Syria and Iraq to Germany, which is home to an estimated one million ethnic Kurds.

"We're watching this very closely," Interior Minister Thomas de Maiziere said in an interview to appear Sunday in German daily Focus.

Those who take part in fighting "should expect a very tough reaction," he warned.

Meanwhile, several thousand people also protested Saturday in Paris and several hundred in the central French city of Lyon to call for international support for Kurds trapped in Kobane.