Apple and Google have been accused of helping to "enforce gender apartheid" in Saudi Arabia, by offering a sinister app which allows men to track women and stop them leaving the country.

Both Google Play and iTunes host Absher, a government web service which allows men to specify when and how women can cross Saudi borders, and to get close to real-time SMS updates when they travel.

Absher also has benign functions — like paying parking fines — but its travel features have been identified by activists and refugees as a major factor in the continued difficulty women have leaving Saudi Arabia.