Police in Britain have launched an international search for a Sikh man suspected of murdering a British schoolgirl and fleeing to India four days later.

"We have a strong suspect for the abduction, rape and murder of Hannah Foster. We do not intend to name this individual at present, but we believe he left the country on March 18 and travelled to India. This was four days after Hannah was abducted," a Scotland Yard authority said.

"We are liaising with Interpol, airports and immigration services to locate this man and return him to the UK," Detective Inspector Tony Adams, in charge of the inquiry, said.

Seventeen-year-old Hannah, an A-level student, vanished on March 14, a few hundred yards from her home in Southampton after seeing a friend on to a bus following a night out.

Minutes later, an emergency 999 call was made on her mobile phone. Police say the muffled voice of a man was heard.

A post mortem examination revealed that she had been strangled out, but until Saturday police said there were no signs that she had been sexually assaulted.

A man was seen dumping her bag in the Southsea area of Portsmouth the next morning and her body was found a day later.

Police acted after a tip-off from a member of the public following a public appeal on the BBC Crime-watch UK programme.