A campaign rally for Syria's President Bashar Assad was hit by mortar fire Thursday evening, as rebels struck the event in the southern city of Daraa. At least 21 people died in the attack, which comes weeks before Syria's presidential election.

From Beirut, Alison Meuse reports for our Newscast unit:

"Mortar fire slammed into a pro-Assad electoral tent. The Syrian Observatory for Human Rights said 21 people were killed in the attack. The dead included a child and six loyalist militiamen."State media called the attack a terrorist act. Rebels frequently lob mortars into government-held areas. And the regime carries out air raids and barrel bomb attacks on opposition territory. The U.N. says both sides are guilty of targeting civilians. But this is the first assault on an election rally."After this latest attack, activists say warplanes dropped leaflets over the city with a message to rebels. They read: 'You have 10 hours to surrender: either leave your arms and return to the bosom of the nation, or go to hell.' "

Assad is widely expected to win a third term in the June 3 election, which many view as a plebiscite, Meuse reports.

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