Sudan's president has freed his former ally, Islamist leader Hassan al-Turabi, who was detained last year in connection with an alleged coup plot.
Turabi used to be a close ally of President Bashir
Mr Turabi said the government had only him freed under pressure and would not be surprised if he was rearrested.
He is a controversial figure in Sudanese politics and has spent much of the last five years in detention.
President Omar al-Bashir said he would also lift the state of emergency that has been in force for six years.
Mr Turabi - a proponent of Sharia law - was once a close colleague of President Bashir but he lost out in a power struggle between the two in 1999.
His most recent spell in detention began in March last year, amid government allegations that he had been involved in a foiled coup attempt in September 2003, which he denies.
"I may go back to prison again. So my coming out is something transient," he told Reuters news agency.
According to the BBC's Alfred Taban in Khartoum, the septuagenarian looked in good health as he waved to some 50 supporters gathered at his party headquarters shouting: "God is great".
The move comes as an interim government prepares to take over on 9 July as a result of the peace deal between the government and southern rebels.
Our correspondent says the president was left with no alternative but to free the Islamist leader because the southern rebels were calling for his release.
President Bashir is attempting to rally all Sudanese around the national unity government and peace deal signed in January, which ended 21 years of civil war in the south, he says.
"[On] 9 July, God willing, will see the signing of the constitution that will govern the transitional period," Mr Bashir said in a televised speech, marking the 16th anniversary of the coup which brought him to power.
He added that after this the state of emergency would be lifted in all regions except Darfur and two areas of eastern Sudan, where fighting with rebels continues.
Mr Turabi's release is a risk for the government, our correspondent says, as he is linked with the creation of the Justice and Equality Movement (Jem) rebel group.
Jem has been fighting pro-government militia in Darfur in the west and is accused of being behind the recent attacks in the east.
Earlier on Thursday, a ban on the activities Mr Turabi's Popular Nationalist Congress was lifted, but the party has said it will not join the new unity government and will remain in opposition.
Mr Turabi fell out with Mr Bashir following the introduction of a bill to limit the president's powers in 1999, a move which the president resisted by dissolving parliament and declaring a state of emergency.
Since then, Mr Turabi's outspoken style has led to him spending most of his time either under house arrest or in prison.