The Sudanese army has removed veteran president Omar al-Bashir from power and detained him, Defence Minister Awad Ibnouf announced on state television on Thursday.

"I announce as minister of defence the toppling of the regime and detaining its chief in a secure place," Ibnouf said.

Bashir, who ruled with an iron fist since he took power in an Islamist-backed coup in 1989, was ousted after deadly force failed to end four months of nationwide protests for his ouster.

"We have replaced him by a transitional military council for two years and have suspended Sudan's 2005 constitution," Ibnouf said, reading from a statement.

"We announce a state of emergency across the country for three months, and we have ordered the closing of the country's borders and airspace until a new announcement is made."

Ibnouf said the military council had also declared a nationwide ceasefire, that includes the war-torn regions of Darfur, Blue Nile and South Kordofan where Bashir's government had long been battling ethnic minority rebels.