By Ulf Laessing UM RAWABA, Sudan (Reuters) - The line of army pickup trucks rumbled into the dusty streets of Um Rawaba, a once placid city in the heart of Sudan that days ago became a new front in the war of attrition between government and rebels. Six days earlier, hundreds of insurgents had stormed in, spraying bullets and killing up to 13 civilians and soldiers, before pulling out as government planes started flying overhead.

KHARTOUM (Reuters) - One Ethiopian peacekeeper was killed and two others wounded when a U.N. convoy was caught up in a tribal clash in the Abyei border region claimed by both Sudan and South Sudan, the United Nations said on Sunday. Sudan and South Sudan in March agreed to resume cross-border oil flows and defuse tensions which have plagued them since the South seceded in 2011 after an independence vote.

Tension and anger on Sunday gripped the Abyei region disputed by Sudan and South Sudan after the killing of a tribal chief and at least one peacekeeper, residents said, as the UN boosted security. The Sudanese foreign ministry condemned the "isolated incident" which killed Kual Deng Majok, the top Ngok Dinka leader in Abyei. Khartoum said members of the Misseriya tribe, the other dominant group in the area, also died in Saturday's incident, along with three peacekeepers from the UN Interim Security Force for Abyei (UNISFA).

Tension and anger on Sunday gripped the Abyei region disputed by Sudan and South Sudan following the killing of a top tribal chief and an Ethiopian peacekeeper, residents said, as the UN stepped up security. United Nations Secretary General Ban Ki-moon called for calm after the Ngok Dinka chief Kual Deng Majok and the peacekeeper died in an "attack" by a Misseriya tribesman in the region on Saturday. "It looks like Dinka are very angry," one local resident told AFP. He reported fire coming from the Abyei town centre, where Misseriya operate small shops.