Security forces firedtear gas on Sunday as thousands of demonstrators took to the streets of the Sudanese capital demanding a return to civilian rule, AFP correspondents said. Raising Sudanese flags and posters of activists killed during pro-democracy protests, protesters tried to march on the presidential palace in central Khartoum as security forces used tear gas to disperse them. Others chanted against military rule and erected barricades in North Khartoum and Omdurman, an AFP correspondent said. Tear gas was also fired in the capital’s twin city of Omdurman and in North Khartoum, where pro…