German Chancellor Angela Merkel attends an event to commend volunteers who are helping refugees and migrants in April this year | Sean Gallup/Getty Images Angela Merkel: ‘No doubt’ some refugees are a security threat ‘We will never accept terror,’ German chancellor said.

Berlin must implement measures to deal with migrants who seek to abuse Germany's willingness to help them, German Chancellor Angela Merkel said.

"We will never accept terror," Merkel told Funke Mediengruppe in an interview published Thursday.

The chancellor acknowledged "there is no doubt" some refugees who have fled war zones pose a security threat to Germany. But she added that the country "was already a target for Islamic terrorism before the many refugees came to us."

Merkel said that while German authorities were doing everything in their power to protect citizens, some regions are lagging in the fight against terrorism and said inconsistencies needed to be resolved. Bavaria allows preventive police monitoring of high risk people, but Berlin and North Rhine-Westphalia ban the practice, she said.

Her comments come days after German authorities arrested a person in connection with explosions that hit a bus carrying the German football team Borussia Dortmund on Tuesday evening. Three documents were found close to the crime scene, and are being examined for Islamic terror links.