More than 30 universities have introduced new rules banning female students from almost 80 different degree courses.

These include a bewildering variety of subjects from engineering, nuclear physics and computer science, to English literature, archaeology and business.

No official reason has been given for the move, but campaigners, including Nobel Prize winning lawyer Shirin Ebadi, allege it is part of a deliberate policy by the authorities to exclude women from education.

"The Iranian government is using various initiatives… to restrict women's access to education, to stop them being active in society, and to return them to the home," she told the BBC.

Higher Education Minister Kamran Daneshjoo has sought to play down the situation, stressing Iran's strong track record in getting young people into higher education and saying that despite the changes, 90% of university courses are still open to both men and women.

Iran was one of the first countries in the Middle East to allow women to study at university and since the Islamic Revolution in 1979 it has made big efforts to encourage more girls to enrol in higher education.

The gap between the numbers of male and female students has gradually narrowed. In 2001 women outnumbered men for the first time and they now make up more than 60% of the overall student body.