BERLIN (AP) — German police carried out raids Thursday against biker groups in several western cities in connection with three killings.

Tactical operations units and hundreds of regular officers conducted raids in Duisburg, Moenchengladbach, Leverkusen and Muelheim an der Ruhr, police said in a statement.

German news agency dpa reported that at least 20 premises were searched.

Prosecutors said the biker groups are linked to the Hells Angels and some are suspected of being involved in two killings in 2013 and a third in 2014, in which the dismembered torso of a former biker group member was found floating in the Rhine River.