More than a dozen soldiers have been killed in clashes in Sudan’s contested Abyei area, Sudanese officials said on Tuesday. The fighting broke out Sunday afternoon when a convoy of northern Sudanese troops tried to enter the specially demarcated Abyei area, which straddles the border of northern and southern Sudan and is administered jointly. Southern Sudanese policemen traded fire with the northern troops; each side says the other one started it. Southern Sudan is preparing to split off from northern Sudan this summer, but Abyei’s status is unresolved. Both sides have been beefing up their military forces in Abyei, raising fears of an all-out border war.