Teen superstar JUSTIN BIEBER is under investigation for assault in his native Canada after allegedly striking a woman while playing with a toy gun, according to reports.

Editors at TMZ.com claim a formal complaint was filed against the Baby hitmaker in November (12) by a female security guard working at the Scotiabank Place in Ottawa, where the singer was performing, after she was hit with a foam missile from a Nerf dart gun Bieber had been using while play fighting backstage with his younger brother and sister.

The woman, whose identity has not been revealed, was so incensed by the incident, she went straight to police - and now officers are looking into the bizarre case.

According to TMZ, cops have already interviewed other venue staff over the mishap, although it is not yet known whether Bieber will have to sit down with authorities to explain his side of the story.