The principal of an Oxford college has launched an appeal for her youngest student, who has been missing for 11 days, to get in touch.

Child genius Sufiah Yusof, 15, pictured right, who is reading maths at St Hilda's College, has not been heard of since June 23, when she telephoned her college dean to say she was staying with a friend. Police are now liaising with the college to see if they can trace the call. At a press conference yesterday, principal Elizabeth Llewellyn-Smith appealed for Sufiah to come forward.

She said: "I would urge Sufiah to get in touch. Her family is naturally very worried.

Sufiah's parents, Farooq and Halimahton, of Coventry, say they are still in the dark about their daughter's whereabouts and have urged her to contact them.

Concern is growing for the talented student, who has been missing from her accommodation in Oxford, after completing her final exam of the year at Oxford University. Anyone with information can call police on 01865 266000.

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"As far as her academic work is concerned, her tutor says she was working well and was not worried about her examinations."

Miss Llewellyn-Smith said there was no indication that Sufiah was not coping with her studies because of her age.

"I think problems would have emerged in the first term she was here," she said.

She said: "My appeal is for Sufiah or her friends to get in touch and to tell us that she is safe and well."

When asked why it had taken so long to launch an appeal for the student to make contact, the principal explained: "We assumed that whatever this protest was about, she would be back.

"It could be a case of someone wanting to stretch their legs, but the longer someone remains out of touch, the more worried you become."

Miss Llewellyn-Smith said Sufiah had been carefully assessed when she first came to Oxford so that special care arrangements could be made, with a member of her family looking after her in her flat.

Thames Valley Police have appealed for Sufiah's safe return and for anyone who knows of her whereabouts to contact with them.

Spokesman Duncan McGraw urged Sufiah to get in touch, either with her parents, the police or the missing person's helpline on 0500 700 700.

He said: "We are very keen to trace Sufiah to put her parents' minds at rest."

Sufiah, who joined the university three years ago aged 13, failed to meet colleagues and tutors for lunch following this year's final exams in Oxford. She still has another year of her course to complete.

In her third year of a four-year Masters course, Sufiah is said to have telephoned her college dean two days after her final exam on June 21, to say she was staying with friends and was all right.

Mr McGraw added: "We have every reason to believe this call was genuine, and are trying to establish where it came from."