The leader of Sudan's largest opposition party, Sadiq al-Mahdi, called on the government to bow to mass protests and resign as he addressed hundreds of supporters Friday in a mosque across the River Nile from Khartoum.
Hundreds of protesters then marched through Omdurman after Friday prayers, until police fired tear gas to try to break up the rally.
Students, activists and other protesters have mounted almost daily protests across Sudan since Dec. 19, calling for an end to economic hardships and mounting the most sustained challenge to President Omar al-Bashir's three decades in power.
"The most important demand is that this regime must leave and be replaced by a transitional government," Mahdi said at the mosque, which has links to his Umma Party.
The former prime minister expressed support for the protests and condemned security forces' use of live bullets, saying 50 people had been killed since unrest began. The official death toll stands at 30, including two security personnel.
Bashir has blamed the protests on foreign "agents" and challenged his rivals to seek power through the ballot box.