Police are hunting for the roommate of a gunman who killed at least 20 people attending a concert in Las Vegas.

The city's police force said the suspect was a local resident whose identity they know but have not released.

They are now searching for a 62-year-old woman named as Marilou Danley.

A gunman on the 32nd floor of a Las Vegas Strip casino opened fire on an outdoor music festival.

Concert-goers reported hearing what they described as automatic gun fire during the shooting.

Thousands fled as bursts of gunfire could be heard for more than five minutes.

A police handout said Ms Danley was being sought for questioning and urged the public to call 911 - the US equivalent to 999 - if she is spotted.

Clark County Sheriff Joseph Lombardo described her as Asian, 4 foot 11 inches tall, 111 pounds (50 kg).

He gave no details of whether she was suspected of involvement in the attack but described her as an "associate".

A Hyundai Tucson vehicle is also being searched for, which is understood to be owned by Ms Danley.

Her LinkedIn profile says she was a "gambling and casino professional" who lived in Reno, Nevada.

Between 2010 and 2013 she worked as a "hostess" for the Atlantis Casino Resort Spa. There is no listing for her employment since that date.

A spokesman for the Las Vegas Metropolitan Police Department confirmed in a news conference on Monday morning that they were yet to locate her.