The Sudanese authorities said four people were killed on Friday evening in protests at various areas of capital Khartoum, bringing the total death toll of the four-day riots to 33, local media reported Saturday. \"Unknown gunmen opened fire at groups of protesters in Khartoum, Bahry, Karary and Umbada localities which resulted in the death of four citizens,\" said the Sudanese police in a statement published by local media on Saturday. Al-Muiz Hassan Bakheet, spokesman of Khartoum State\'s Health Ministry, meanwhile, was reported to have said that Khartoum hospitals have received so far 300 injured people due to the protests, 111 of them are policemen. The authorities on Friday evening used tear gas to disperse protesters at Shambat area in northern Khartoum and clashed with protesters following Friday prayer at areas in Omdurman and Khartoum. Hundreds of people are still staging protests at Buri and Al- Siteen Street in Khartoum while the police and security authorities confronting them with tear gas. No casualties have been reported so far. On Thursday, the Sudanese police said that 29 people, including civilians and policemen, had been killed since last Monday during the protests in Khartoum and Gezira. Last Monday, the government announced a fuel price hike as part of economic reforms aimed at reviving the country\'s economy, which led to eruption of protests in Khartoum and other areas. Sudan\'s economy has been suffering from difficulties after losing two thirds of oil resources following the separation with South Sudan in 2011.