A 66-year-old woman is in critical condition after a knifeman shouted “Allahu Akbar” (“Allah is the greatest” in Arabic) and attacked her and her partner at a music festival in Germany. After his arrest, the attacker was taken to a psychiatric clinic.

Local German media reported that the attacker went on a “rampage”, harassing festival-goers, before grabbing a knife from the couple’s own picnic and stabbing a 66-year-old woman and a 57-year-old man, reportedly whilst shouting: “Allahu Akbar”.

The 57-year-old was injured in the attack, but the woman, believed to be the other victim’s wife, suffered serious injuries and is in hospital fighting for her life.

The attack occurred at the Oberhausen music festival some time after 7pm on Saturday night. Despite his injuries, the 57-year-old, assisted by a police officer and a member of the fire brigade, was able to overpower the assailant after the attack. The victim claimed that during the attack the knifeman shouted “Allahu Akbar”, an Arabic phrase meaning “Allah is the greatest”.

Witnesses, including many young people who were at the evening festival, are being treated for shock.

The assailant has been identified as a 26-year-old of no fixed abode, from the Duisburg area. The International Business Times reported that the attacker was taken to a psychiatric clinic following questioning.

In a statement, police said the suspect was “apparently under the influence of narcotics“, but despite the victim’s statement that the attacker shouted “Allahu Akbar” during the stabbing, police spokesman Andreas Wilming-Weber said said no other witnesses heard the phrase, adding that there was “no indication of any political motive”.

Europe has experienced a spate of seemingly ‘lone-wolf’ Islamic State-inspired attacks, with the attackers shouting “Allahu Akbar” during the attacks.

Earlier this month a Jewish man in Strasbourg, France, was hospitalised after being stabbed by a man who was claimed to have shouted “Allahu Akbar”. In June a terrorist shouted “Allahu Akbar” as he stabbed a police officer and his wife to death near Paris, the attack later being claimed by Islamic State.

Also in May in Munich a man shouted “Allahu Akbar” as he attacked commuters on a train, leaving one dead and three injured; the 27-year-old was also reported to have had “drug problems and [had been receiving] psychiatric treatment”.

This is the latest in a series of potential Islamic terrorism-inspired incidents that have been attributed to “substance abuse” or mental health.

Following the fatal stabbing of an American tourist and injury of five others by a Norwegian passport holder of Somali origin in London, the public took to Twitter to mock the police pursuing “poor mental health” as a line of enquiry. A prominent Austrian psychiatrist had also blasted the media for “lumping in” terrorists with those who genuinely suffer from mental health issues.