German police say they have arrested 10 people in the west of the country on suspicion of planning an Islamic extremist terror attack.

The dpa news agency reported the suspects were taken into custody on Friday and Saturday in the towns of Essen, Duesseldorf, Wuppertal, Moenchengladbach, Duisburg and Ulm, citing a spokesman for prosecutors in Duesseldorf.

The prosecutors' spokesman was quoted as saying Saturday that the group was suspected of a connection to the Islamic State group, either as sympathizers or a splinter group, and of planning a "serious act of violent subversion," although there was currently no indication of a specific target. Prosecutors were not yet certain if criminal cases would be brought against all those taken into custody.

Officials said one of the suspects was from Tajikistan but provided no information about the nationality of the others.