Nigeria's secret service say they have arrested a "terrorist cell" trained in Iran who planned to attack U.S. and Israeli targets in Africa's most populous nation, according to Reuters.

The State Security Service (SSS) said they arrested Abdullahi Mustapha Berende and two other Nigerians in December after Berende made several suspicious trips to Iran where he interacted with Iranians in a "high profile terrorist network".

"His Iranian sponsors requested that he identifies and gathers intelligence on public places and prominent hotels frequented by Americans and Israelis to facilitate attacks," SSS spokeswoman Marilyn Ogar said in a statement.

"There is conclusive evidence that Berende in collaboration with his Iranian handlers were involved in grievous crimes against the national security of this country."

Iran has yet to respond to the allegations.

Berende, who will now be charged in court, admitted spying for Iranian counterparts to reporters on Wednesday.

"As for surveillance, that one is true ... It is a regrettable phenomenon I shouldn't be proud of it," he said as he was paraded by the SSS in their Abuja offices.

He received $30,000 to carry out operations, the SSS said.