At least 20 people were reported killed overnight in the Sudanese capital as clashes between northerners and southerners extended to a third day on Wednesday after the death of former southern rebel leader John Garang. Violence in Khartoum erupted on Monday when angry southerners took to the streets after the official announcement of the death in a helicopter crash of Garang, who fought the northern government for two decades before making peace. "There are quite a number of casualties and it's quite serious," U.N. spokeswoman Radhia Achouri told Reuters. Some southerners fear the absence of Garang, who was made Sudan's first vice president last month, could weaken their hand in governing Africa's largest country.