The Home Office is not confirming or denying whether any British workers have been involved.
But officials say they are investigating reports which suggest at least one Briton was taken when gunmen stormed a compound belonging to a Lebanese construction company in Nigeria.
ITV News reporter Sejal Karia talks from outside the Foreign Office:
More top news
Deputy party leader Tom Watson said that what has happened with Jeremy Corbyn is a "great tragedy".
A father who must give police 24 hours' notice before he has sex is planning to go on hunger strike in protest at the "extreme" order.
Remaining unsettled over the next few days.