Sudan's ruling military council said it had foiled a coup attempt, with 12 officers and four soldiers arrested so far.
The announcement on Thursday came as the military and civilian protesters discussed details of an agreement reached 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 Ibrahim of the Transitional 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.
Witnesses described a heightened security presence in the capital, Khartoum, with troops positioned at key bridges, intersections and the main radio station.
Gen Omar said of the five of the 12 officers arrested 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," Gen Omar said.
The coup bid was revealed as generals and protest leaders went through the details of the agreement at a luxury hotel in Khartoum. The two sides held intense discussions through the night into the early hours of Friday and later agreed to continue on Saturday, mediators told reporters.
The landmark agreement that aims to form a new joint transitional civilian-military ruling body was reached last week after intense mediation by African Union and Ethiopian envoys.
The forming of the new governing body is the first step towards installing an overall transitional civilian administration in Sudan as demanded by demonstrators.
Sudan has been rocked by a political crisis since protests first erupted against Mr Al Bashir's rule in December.
The protests finally led to the army ousting him on April 11, but the generals who seized power have so far resisted demonstrators' demands to hand it over to a civilian administration.
Tension had further soared between the two sides after a brutal raid on a longstanding protest camp outside army headquarters in Khartoum on June 3 that killed more than 100 demonstrators and wounded hundreds of others.
The raid came after talks between the generals and protest leaders collapsed in May over who should lead the new governing body – a civilian or soldier.
Mediation by the AU and Ethiopia finally led to agreement on a joint governing body on July 5.
The agreement proposes a transition period of just over three years, with the presidency of the ruling body to be held by the military for the first 21 months and a civilian for the remaining 18 months.
The ruling body will comprise of six civilians, including five from the protest movement, and five members of the military.
