A businessman is being hunted in connection with the murder of a party-loving student after they were seen together at a London nightclub on the night she disappeared.

Martine Vik Magnussen, 23, was allegedly seen leaving the members-only club Maddox, in Mayfair, in the early hours of Friday with an Arab friend.

The Norwegian student’s body was found on Sunday morning in a basement at Seaford Court, an apartment block in Great Portland Street, Central London. A postmortem examination revealed that Ms Vik Magnussen had died from severe neck injuries. An exact cause of death has yet to be established.

An anonymous source told the Norwegian news agency NTB that the victim and her friends used to go out with rich Arab men in London. The men were regulars at Maddox, which has attracted celebrities such as Madonna, Keira Knightley and P Diddy since it opened last year.

“The man she was hanging out with, the victim’s friends have not been able to contact,” a source told NTB.

Detective Chief Inspector Jessica Wadsworth, who is leading the investigation, said: “She was a very popular young woman with lots of friends and had a vibrant personality. We are keen to retrace her final movements and would appeal to anyone who was with her that night or has any information to assist the inquiry.

“We would like to speak to a number of people in relation to her death, including a man of Arab appearance who was among her group of friends on Thursday night and who she may have left the club with in the early hours of Friday.”

Residents of Seaford Court said that police were searching a flat in the block that was being rented at £600 a week. Jane Morrison, 72, said: “The forensics [officers] have been here all day. I’m not allowed to go to the basement where we take our rubbish. It’s really dreadful. The people who have the flat have lots of parties that drive me nuts.”

Miss Magnussen moved to London in February last year and has been studying business at the private Regent’s Business School, Regent’s Park, since November.

The student – a close family friend of Norway’s richest man, John Fredrikson – had become a regular on the London party scene. Two friends who lived with Miss Magnussen in Westminster issued an urgent appeal for any information on Facebook after she failed to return home.

Thale Lassen and Nina Brantzeg said: “Martine was at Maddox club in London [on] Thursday March 13. Her flatmates went home at 2.30am while she decided to stay at the club with some other friends.

“She was last seen in the club at 3am. We need information from anyone that might have seen her or heard where she was going after the club.”

A friend said that she had sent a message via Facebook to an Arab businessman listed on Miss Magnussen’s page asking if he knew what had happened. She told Norwegian media: “I wrote: ‘Do you know where she is?’ I got no answer and shortly thereafter his profile was deleted.”

Miss Magnussen is from Nesoya, an island outside Oslo that is home to Norwegian celebrities and business-men. Her divorced parents, Odd Patter Magnussen and Kristin Vik Ronnaug, her brother, Magnus, 24, and a sister, Mathilde, have flown to London.

The murder has caused concern among the 500 Norwegian students living in London. The Norwegian Seamen’s Church and the Norwegian Student Association in London have opened a crisis telephone line to offer counselling. Birgitte Ardal, a member of the association’s board, said: “Although murders are being committed almost on a daily basis in this city, we are being very shaken when it takes place in the Norwegian community.”

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