The parents of missing Oxford student Sufiah Yusof appealed to her today to get in touch, writes John Chipperfield.

The 15-year-old child genius vanished after taking a three-hour maths exam and has not been seen for 12 days.

She had been due to meet her personal tutor, Dr Irene Ault, and fellow students for lunch at St Hilda's College the day after the exam, but did not turn up.

A blurred image on Oxford's CCTV system shows someone similar to Sufiah, on the day she disappeared, with a man whose face is covered with an umbrella. He was pulling a black trolley suitcase, identical to one in which Sufiah had packed her clothes.

Sufiah, one of five children, started at St Hilda's at 13 after being taught at home by her Malaysian-born parents, Farooq and Halimahton Yusof.

Mr Yusof, 43, of Northampton, said: "Everyone is simply shattered. Our lives have been turned upside down. We can't sleep. We just cannot understand why she has vanished. "We have spoken to her friends at college, her lecturers, her brothers and sisters nobody had any inkling anything was wrong. We are living every parent's worst nightmare."

Mrs Yusof, 44, said: "She seemed so happy. There was nothing to suggest anything was wrong."

Sufiah, a devout Muslim, who is in the third year of a four-year maths degree course, was last seen on June 21. When college staff searched her room, they found clothes scattered on the floor and her prayer mat and mobile phone. Sgt Jim Sudworth, of Oxford police, said: "It would appear there is no rhyme or reason for Sufiah to go missing. We have made extensive inquiries through all the colleges in Oxford. As yet, there is absolutely no trace of her.

Obviously as time goes by, our concern grows."