Britain has warned its citizens in Nigeria to stay away from northern parts of the country where Islamist militants have threatened to attack and abduct nationals from Western countries.
The warning came against the background of the threats by Islamist groups which posted their threats on the Internet.
A statement from the foreign office, advised "against all-but-essential travel" to Kaduna, Kano, Jigawa and Katsina states.
Britain upped its travel risk ratings on Wednesday, advising against any travel to Bauchi State and Okene city in southern Kogi State where militants last month attacked Nigerian troops who were bound for Mali to counter an Islamist insurgency.
Britain put Ansaru on its official "terrorist group" list in November , saying it was aligned with al Qaeda and was behind the abduction of a Briton and an Italian killed last year during a failed rescue attempt.
Western governments are concerned the militants may link up with groups elsewhere in the region, including al Qaeda's North African wing AQIM, especially given the conflict in nearby Mali. France sent troops to Mali last month to help oust Islamist rebels.