Khartoum - Sudanese opposition leader and ex-prime minister Sadiq al-Mahdi will return to the country on Thursday more than two years after he fled abroad, a senior official in his party said.Mahdi, whose civilian government was overthrown in the 1989 Islamist-backed coup that brought President Omar al-Bashir to power, has been in self-imposed exile, mainly in Cairo."Sadiq al-Mahdi will return today after an absence from the country of 30 months," the deputy head of his Umma party, Fadlallah Burma Nasser, told AFP.Mahdi, 81, is expected to fly into Khartoum airport and later make a speech to supporters.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. Mahdi had been arrested after accusing pro-government paramilitary forces of rape in western Sudan's Darfur region.The case sparked concern from Western governments but Mahdi was released after his legal team appealed to the justice minister to drop or suspend the charges. The exact status of the charges is not clear.A fixture of Sudanese politics since the 1960s, Mahdi was prime minister from 1966 to 1967 and again from 1986 to 1989.The Umma party is one of Sudan's oldest political institutions. Mahdi is also revered by followers in his Ansar al-Islam movement, a key component of the party.While in exile Mahdi signed a controversial agreement joining Umma in an alliance with other opposition parties and a number of rebel groups from the war-torn Blue Nile, South Kordofan and Darfur regions.In a statement in November Mahdi had called for a three-day nationwide strike against Bashir's regime, amid mounting anger over fuel subsidy cuts and other economic problems.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.