Sudan's army has committed the first serious violation of a final ceasefire signed a year ago to end Africa's longest civil war in its south, a UN peacekeeping official said on Wednesday. The former southern rebel Sudan People's Liberation Movement (SPLM) said the army sent around 1,200 troops last week into the rebel-controlled eastern area of Hamesh Koreb and has threatened to expel the SPLM. A joint UN-led team is still in the area to defuse tensions between the two sides.