The electoral commission for the southern African nation said poll workers had been attacked and ballots had been stolen as both top candidates claimed leads.

Kevin Rideout, a pilot, had been abducted from his home in the country’s capital, Niamey, last fall. His mission organization said he was in “good health” after his release.

Taking El Obeid would allow the paramilitary Rapid Support Forces to consolidate its hold on western Sudan, a significant strategic goal.