A 16-year-old Syrian refugee has been arrested in Germany on suspicion of having ties to the ISIL group, officials said Wednesday, describing him as a "serious threat".

The youngster, thought to have been radicalised only recently, was detained in a special forces operation late Tuesday at a shelter for asylum seekers in the western city of Cologne, police and local prosecutors said in a statement.

Information gathered from the teenager's mobile phone indicate he was in touch with a person abroad who had ties to IS and "wanted to recruit the young Syrian for terrorist activities", the statement said.

Germany's state security authorities believe the youngster posed a "serious threat" and have assigned a 35-strong team of investigators to the case.

Germany is on edge after suffering two attacks claimed by IS in July -- an axe rampage on a train in Wuerzburg and a suicide bombing in Ansbach. Both were carried out by asylum seekers.

In Wuerzburg, the 17-year-old attacker was shot dead by police after injuring five people.

In Ansbach, 15 people were injured after a Syrian failed asylum seeker detonated an explosive device outside a music festival, killing himself.

The attacks rattled Germans' sense of security and fuelled concerns over the country's record influx of migrants and refugees last year; AFP reported.

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