Police investigating the murder of an American artist who was stabbed to death in a London park say two men were seen running from the scene.

Detective Chief Superintendent Jon Shatford described the news as a "very active" line of inquiry into the killing of Margaret Muller, 27.

The men, described as "of eastern Mediterranean appearance" were seen running from the rose gardens in Victoria Park, near where Miss Muller was found, towards nearby Guinness Road in Hackney.

They appeared to check each other's appearance and clothing before resuming at a slow walking pace, police said.

As a student, Miss Muller painted to earn money

One was described as holding his head down and the witness thought he was trying to hide his face.

Miss Muller, who was 4ft 10in tall, was stabbed in the body and neck, apparently while out jogging on Monday morning.

"We are extremely keen to speak to anyone who may have seen these men in or around Victoria Park, " said Mr Shatford.

"We consider this to be highly significant at this time but there are other lines of inquiry that we are also following."

He added that the cyclist they wanted to trace had since come forward and helped police.

The BBC's Crimewatch programme is also planning to make an appeal on Wednesday night's show.

Miss Muller moved to London from the United States in 1998 and studied and worked at the Slade School of Fine Art.

"We have to consider the possibility of the attacker being a total stranger" DCS John Shatford, Metropolitan Police

As a student she supplemented her income by painting and had a studio in a converted factory in Hackney in which she lived.

Police eventually identified her by calling a friend whose number was on her mobile phone.

Officers are arranging for her parents, who are said to be "extremely shocked", to come to London.

Her father Erich told the Daily Telegraph newspaper she wanted to be a great artist.

He said: "She liked London very much.

"She had just moved to Liquid Studios. She was aware that it wasn't a terribly desirable area but she didn't feel particularly unsafe.

No weapon has been found and there is no evidence that Miss Muller was sexually assaulted.

Mr Shatford said the police were carrying out a complete profile of her life as part of the investigation.

He added: "We would like to know anyone in the area who knows someone whose character has changed or is in any way different or that they are suspicious of, because we have to consider the possibility of it (the attacker) being a total stranger."