German police have arrested 10 suspected militants on suspicion of terrorism following searches in the western states of North Rhine Westphalia and Baden-Wuerttemberg.

They are being investigated on suspicion of planning a serious crime endangering the state, a spokesman for prosecutors in Dusseldorf said on Saturday.

While there is no evidence of concrete targets or a concrete act, authorities are looking into possible connections to the Islamic State extremist group, the spokesman said.

‘We assume that it is a splinter group of IS (Islamic State) or sympathizers,’ he said.

The raids took place in the cities of Essen, Dusseldorf, Wuppertal, Moenchengladbach, Duisburg and Ulm from Friday morning until Saturday morning.

‘We have to see if what we found is what we were looking for,’ the spokesman said.

It was not clear if warrants had been issued for the 10 suspects.

One of the suspects is from Tajikistan, while the nationality of the other suspects is unknown.