ABUJA (Reuters) - Nigerian police have uncovered a plot to bomb the Abuja transport network, they said on Saturday, using suicide bombers and devices concealed in luggage at major bus stations.

Abuja has increasingly been targeted by Islamist group Boko Haram, with three deadly bombings since April, including one in a bus park on its outskirts that killed at least 75 people.

"Credible intelligence ... indicates that terrorists have perfected a plot to carry out attacks on the Abuja transport sector ... intended to cause panic amongst Abuja residents and visitors," police spokesman Frank Mba said in a statement.

Boko Haram militants, fighting for an Islamic state in religiously-mixed Nigeria, have killed thousands of people since 2009 and made world headlines with the abduction of more than 200 schoolgirls in the northeast village of Chibok on April 14.

On the same day, the bus park attack - which took place less than a month before Nigeria was due to host the World Economic Forum - killed 75 in what was the first bomb in Abuja for nearly two years.

There have been two deadly attacks in Abuja since then, including one in the upmarket shopping district of Wuse II.

"The Police High Command has called on the management of motorparks to ... constantly conduct regular and routine scanning of their environments while insisting on carrying out a thorough search on passengers and their bags as well as vehicles," the statement said.

The Islamist insurgency had been largely confined to the north until a suicide bomber attacked Abuja's police headquarters in June 2011, killing several people.

Two months later a suicide truck bomb targeting the U.N. headquarters in Abuja killed 25 people.

(Reporting by Tim Cocks; Editing by Lynne O'Donnell)