Sudan detains prominent opposition politician KHARTOUM (Reuters) - Sudanese security forces detained one of the country's most prominent opposition politicians, Farouk Abu Issa, after he attended an opposition party forum on Thursday, the politician told Reuters. "I'm now in the security agency's offices," Issa said by phone. Issa, head of the National Consensus Forces, an umbrella group of Sudan's main opposition parties, is believed to be nearly 80 years old. There was no immediate comment from the security agency. Arab-African Sudan has avoided the mass unrest that unseated rulers in Egypt and Tunisia, but rising food prices and other grievances have caused smaller protests over the last two years. South Sudan split away from the Khartoum-ruled north in July of last year, taking about three-quarters of Sudan's oil output with it and sending northern Sudan into an economic crisis it has yet to resolve. It was unclear why security forces detained Issa, but he said he was arrested at his home after he had returned from a recent forum held by the opposition Umma Party. Opposition politician Kamal Omar called on the government to release Issa immediately. "We're extremely worried about his health and charge the government with full responsibility for anything that happens to him," he said. Reporting by Khalid Abdelaziz; Writing by Alexander Dziadosz; Editing by Michael Roddy