The Department of State Security (DSS) says it has thwarted a plot by militant Islamist group Boko Haram to attack the UK and US embassies in the capital Abuja.
Six people were arrested last month in connection with the plot, the DSS added.
There has been no independent confirmation of the agency’s claim.
In a statement, the DSS said five of the men had “perfected plans” to attack the embassies.
They were arrested on 25 and 26 March in Abuja and Benue state, the DSS added.
A sixth person was arrested on 22 March in north-eastern Yobe state, and he confessed to being part of the group’s “sinister activities”, the DSS said.
The US embassy in Abuja said it appreciated the DSS’s efforts in “fighting terrorism”, and the US and Nigeria had a “strong partnership in countering violent extremism”.
A UK government spokesman said: “We are grateful for the support we receive from the Nigerian security authorities in protecting UK diplomatic staff and premises in Nigeria. We are in regular contact with the Nigerian security authorities concerning potential threats to UK interests in Nigeria.”
