The announcement came as the ruling military and civilian protesters agreed last week to end a political impasse after the army in April ousted longtime ruler Omar al-Bashir on the back of a popular uprising.
"Officers and soldiers from the army and National Intelligence and Security Service, some of them retired, were trying to carry out a coup," General Jamal Omar of the ruling military council said in a statement broadcast live on state television.
"The regular forces were able to foil the attempt," he said, but did not say when the attempt was made.
Omar said of the 12 officers arrested, five of them were retired, and that security forces were looking for the mastermind of the attempted coup.
"This is an attempt to block the agreement which has been reached by the Transitional Military Council and the Alliance for Freedom and Change that aims to open the road for Sudanese people to achieve their demands," Omar said.
The announcement late Thursday came as legal advisers of the ruling military council and protest leaders were going through the details of the agreement at a luxury hotel in Khartoum.
The landmark agreement that aims to form a new joint transitional civilian-military ruling body was reached last week after mediation by African Union and Ethiopian envoys.
The forming of the new governing body is the first step toward installing an overall transitional civilian administration in Sudan as demanded by demonstrators.--AFP