Adam Levine accidentally nails fan in head with microphone

Maroon 5 lead singer Adam Levine's fury at a faulty PA system turned to panic when the microphone he hurled accidentally clocked a female fan in the head.

Footage obtained by TMZ shows the frontman pacing up and down the stage during a brief power outage at his concert in Toronto on Monday night.

He repeatedly tests the mic for a response before throwing it down in frustration — and then watched it bounce off stage and fly into a front row audience member, later identified as Stephanie Green.

The footage shows Levine immediately apologise to a bruised but unharmed Green, bringing her up on stage and giving her a hug.

"In my flustered state, I might have thrown my microphone on the ground and then it might have bounced off of the ground, into poor, sweet Stephanie's face," Levine told concert-goers.

"I felt so utterly terribly that I had perhaps wounded this young fan."

Green later told CityNews she was thrilled by all the attention she got from her pop idol.

"He keeps apologising," Green said as she watched a replay of the incident. "[I said] 'I love you, I'm happy, I'm OK!'"