Japanese pop star Mayu Tomita stabbed dozens of times by obsessive fan

Tomita has yet to gain consciousness

Before the attack, the singer informed police Iwazaki had been harassing her online and had posted obsessive comments about her on Twitter and blogging sites (Twitter)

A Japanese pop star is in critical condition after she was repeatedly stabbed by an obsessive fan.

Mayu Tomita, 20, is said to have been stabbed dozens of times in the neck and chest after refusing a gift before performing at a concert in Koganei in Tokyo on Saturday afternoon.

The singer, who is a college student, suffered nearly two dozen stab wounds to her neck and chest and has yet to gain consciousness according to reports in the Japanese media.

Tokyo police said a 27-year-old man, Tomohiro Iwazaki, was arrested at the scene by officers, who seized a blood-covered knife.

Before the attack, the singer informed police Iwazaki had been harassing her online and had posted obsessive comments about her on Twitter and blogging sites.

Tomita appears in pop idol shows and television programs for children.

In 2014, two teenage members of Japanese girl pop band AKB48 were attacked by a man brandishing a saw at one of the band's fan events.