KHARTOUM About 600 Sudanese protesters chanted and waved banners and flags after Friday prayers in the capital Khartoum, demanding the release of opposition leader Sadiq al-Mahdi who was arrested two weeks ago.
Mahdi, head of the opposition Umma Party, was detained after the public prosecutor opened an investigation into charges he insulted state security forces over a surge in violence in the western Darfur region.
Mahdi served as prime minister in Sudan's last elected civilian government before he was overthrown by current President Omar Hassan al-Bashir in 1989.
Security forces, including dozens of riot police holding plastic shields, surrounded the demonstrators as they gathered at the Imam Abdel Rahman mosque in the Omdurman district of Khartoum to protest the detention.
"No dialogue with the villains," the protesters chanted. "Sadiq is the voice of the people."
Demonstrators raised Umma Party flags and signs with "Revolution, revolution until victory" and "Release the Imam Sadiq al-Mahdi" written on them.
The two sides did not clash, unlike demonstrations in 2012 and 2013 against Bashir's rule which led to violent confrontations with police.
During his quarter-century in power, Bashir has weathered protests, armed insurgencies, U.S. trade sanctions, the secession of oil-producing South Sudan and an arrest warrant from the International Criminal Court on charges of masterminding genocide and other war crimes in Darfur.
In response to Mahdi's arrest, the Umma Party canceled national dialogue talks called by the president that were meant to ease tension among political parties ahead of parliamentary and presidential elections due next year.
It also called on its supporters to protest the detention, and some of Friday's demonstrators vowed to press ahead. "We will not stop until they release the hope of Sudan, Sadiq al-Mahdi," said Ahmed Awad, 42.
A decision to cut fuel subsidies in September led to riots in which dozens of people were killed and hundreds arrested.
(Reporting by Khalid Abdel Aziz, Writing by Alexander Dziadosz in Cairo, Editing by Alister Doyle)