Sudanese opposition leader and former prime minister Sadique al-Mahdi returned to the country on Thursday more than two years after he fled abroad, his party said.
Mr Mahdi, whose civilian government was overthrown in a 1989 coup that brought President Omar al-Bashir to power, flew in to Khartoum, said his daughter Mariam al-Mahdi, deputy head of the Umma party.
She said that authorities prevented several supporters from entering the airport to welcome Mr Mahdi.
Month in custody
A fixture of Sudanese politics since the 1960s, Mr Mahdi was prime minister from 1966 to 1967 and again from 1986 to 1989.
He left Sudan in August 2014, a few weeks after being released following a month in custody on treason-related charges that could have seen him face the death penalty.
Mr Mahdi had been arrested after accusing pro-government paramilitary forces of rape in western Sudan's Darfur region.
The Umma party is one of Sudan's oldest political institutions. Mr Mahdi is also revered by followers in his Ansar al-Islam movement, a key component of the party.
In a statement in November Mr Mahdi had called for a three-day nationwide strike against Bashir's regime, amid mounting anger over fuel subsidy cuts and other economic problems.
President Bashir, who is wanted by the International Criminal Court on charges of war crimes and genocide related to the conflict in Darfur, has been accused of systematic repression of the opposition.