Nigeria's security forces are on high alert over a planned attack by Islamist militants on public infrastructure in Abuja and Niger states, an internal memo dated April 13 obtained from the Nigeria Customs Service by The Associated Press on Wednesday showed. The planned targets include the international airport and a prison facility in the capital city of Abuja, as well as a military detention centre in neighbouring Niger state.

"Their intention is to release detained terrorists and inflict significant damage on critical aviation infrastructure," the memo reads. The plan mirrors a similar attack in Niger Republic in January, in which Islamist terrorists attacked an air force base in Niamey, the memo read in a warning to customs service personnel.