An oil company working in Nigeria’s restive and oil-rich southern delta said today that five of its employees were kidnapped and two others wounded during an attack on an offshore oil rig.

British diplomats said today they have so far been unable to confirm reports that an oilworker kidnapped in Nigeria has died while still being held hostage.

Nigerian rebels have demanded $40m (€31.5m) for the safe return of four kidnapped British oil workers.