Jesse Matthew, 34, pleaded guilty to the murders of University of Virginia student Hannah Graham, 18, and Virginia Tech student Morgan Harrington, 20, and abduction with intent to defile.

British-born Ms Graham vanished in 2014 and Ms Harrington disappeared in 2009.

Matthew, from Virginia, said he was sorry through his attorney at Albemarle County Circuit Court.

He is already serving three life terms for a 2005 sexual assault in northern Virginia.

Ms Graham's mother, Susan Graham, called her daughter "a heroine" as she had enabled law enforcement to apprehend Matthew who had been "hiding in plain sight in Charlottesville for years".

Ms Graham was born in Reading, England, and moved to the US with her parents at the age of five.

She vanished after having dinner and attending parties away from her university campus in September 2014.

CCTV captured her walking unsteadily past a service station and a restaurant. Footage also showed Matthew walking with her, his arm wrapped around her.

Her body was found five weeks later on abandoned property in Albemarle County, about 12 miles from the Charlottesville campus and six miles from a hay field where Ms Harrington's remains had been found in January 2010.

Ms Harrington disappeared in 2009 after she stepped out of a Metallica concert at the University of Virginia and was unable to get back in.

Matthew, who was a taxi driver before going to work at the University of Virginia hospital, was accused of raping students in 2002 and 2003 at Liberty University and Christopher Newport University, but the cases were dropped when the women declined to press charges.

A spokesman for Matthew's family apologised to the victims' families. Reverent Louie Carr said that "words cannot express our sadness about what happened".

"It's hard to understand how a gentle soul" could commit such crimes, Mr Carr added.