German Chancellor Angela Merkel said security threat level in Germany remained high after Paris attacks.

Two people arrested in Berlin on Thursday had links to ISIS, which may have been planning an attack in the western city of Dortmund, a German newspaper said on Friday, citing security sources.

German police commando units arrested two men aged 28 and 46 on Thursday suspected of planning an attack and searched a cultural center, a police spokesman said.

German newspaper Tagesspiegel said the two men were from Syria and Tunisia and have links to the extremist militant group ISIS. The paper added that security forces suspected ISIS could have planned a possible attack in Dortmund.

Criminal investigations have also been opened into other people, including asylum seekers, in connection with Thursday’s arrests, the paper said.

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