A couple was stabbed at a German musical festival by a man who attacked them while shouting "Allahu Akbar."

The male victim, aged 57 was seriously injured; his 66-year-old wife is said to be fighting for her life. Despite his injuries, the man was able to overpower the attacker who was arrested by police.

The couple was enjoying a picnic when they were attacked.

Police say the attacker was "apparently under the influence of narcotics". The suspect was also described as a 26-year-old homeless man from Duisberg, Germany.

The weapon was recovered from the scene.  Officer are still looking for a motive.

Police spokesman Andreas Wilming-Weber said there is "no indication of any political motive."

A judge ordered the man be put in a psychiatric facility.