Khartoum - About 200 protesters marched on Wednesday in the Sudanese capital's twin city of Omdurman against rising food prices, with anti-riot police firing tear gas to disperse the rally.Prices of food items but mainly bread have surged in past weeks across Sudan after a jump in the cost of flour due to a shortage of wheat supplies.Sporadic protests have since erupted in parts of Sudan, including Khartoum, with demonstrators coming out onto the streets in their hundreds."No, no to hunger! No, no to high prices!" protesters shouted as they marched towards a square in central Omdurman, the twin city of Khartoum on the west bank of the Nile River.Anti-riot police moved in swiftly to stop their march and fired tear gas, an AFP correspondent reported.Authorities had poured water into the streets leading to the square in an attempt to prevent protesters from reaching the site, he said.Wednesday's rally was called by the main opposition Umma Party, a day after a similar demonstration held near the presidential palace in Khartoum following a call issued by the Communist Party.Tuesday's protest was also broken up by police using tear gas and beating protesters with batons.Sudan's powerful National Intelligence and Security Service early on Wednesday arrested the Communist Party chief, Mokhtar al-Khatib, from his home, his party spokesperson told AFP.Several other senior Communist Party figures, student leaders and activists have already been arrested since the bread price protests began earlier this month.The protests erupted after the cost of a 50kg sack of flour jumped from $9 to $25, as wheat supplies dwindled following the government's decision to leave grain imports to private companies.So far they have been sporadic and quickly broken up by security forces. But a student was killed during a protest in the western region of Darfur on January 7.Similar protests were held in late 2016 after the government cut fuel subsidies.The authorities cracked down on those protests to prevent a repeat of deadly unrest that followed an earlier round of subsidy cuts in 2013.Dozens of people were killed when security forces crushed the 2013 demonstrations, drawing international condemnation.