German police say 30 protesters of an ultra-conservative Muslim group were arrested after clashing with security officials.

Police spokeswoman Anja Meis said a group of Salafists protesting against a far-right march threw stones and attacked officers separating the two rallies in the western German city of Solingen Tuesday. Three policemen and a passer-by were injured.

She says the violence erupted after far-right protesters showed cartoons depicting Islam's Prophet Muhammad drawn by Danish cartoonist Kurt Westergaard which were first published in a newspaper in 2005.

Islamic law generally opposes any depiction of the prophet.

Germany's domestic intelligence agencies are keeping a close eye on Salafists, suspected by officials of spreading a radical ideology condoning violence.