A German official says he's tightening checks on security personnel at asylum centers following allegations that private guards repeatedly abused refugees.

Authorities in North Rhine-Westphalia, Germany's most populous state, raided an asylum center last week after a local journalist received a DVD showing guards abusing an asylum seeker. Allegations have since surfaced of abuse at two other facilities.

State interior minister Ralf Jaeger said Tuesday that from now on all people deployed to asylum centers by security firms will first have to undergo a police background screening.

Jaeger said that although refugee arrivals in Germany have increased sharply in recent months and local communities are facing challenges to provide accommodation, "we will not allow people who have come here seeking shelter from persecution and war to be abused."