UN helicopters fired on in Sudan town

Sudan's president gave northern troops a "green light" to attack southern forces if provoked, while gunmen from an Arab tribe fired on four UN helicopters taking off from a disputed border town at the heart of a new north-south conflict, officials said Wednesday. Both Sudan's north and south claim Abyei, a fertile region about the size of Connecticut that is located near several oil fields.

Northern tanks and soldiers rolled into the disputed region Saturday following the attack on a northern army convoy Thursday, raising fears the dispute could trigger a return to civil war in Africa's largest nation.

President Omar al-Bashir said his troops do not need permission from Khartoum to attack southern forces if they feel provoked, the state news agency SUNA said. He accused the U.S. of double standards because he said it protested loudly over the occupation of Abyei by the north, but less loudly over the preceding attack on northern troops and UN forces.

U.S. President Barack Obama, speaking Wednesday at a news conference in London, called for the rapid reinforcement of UN peacekeeping troops in the Abyei region, from which tens of thousands of civilians have fled over the last week.

Southern Sudan voted in January to secede from the north, and it is scheduled to declare independence in July. But the north's occupation of Abyei has greatly strained north-south relations. The two regions fought a two-decade-plus civil war that claimed two million lives.

Northern aircraft are reported to have made bombing runs in the region, and the UN said gunmen set homes ablaze and looted in Abyei town. The accusations were supported by satellite images released Wednesday by the Satellite Sentinel Project, which showed burnt structures north of Abyei town and fires burning in the region. The south's secession vote was promised in a 2005 peace deal that ended the north-south civil war. The conflict over Abyei could scuttle the peace deal that promised the January independence referendum and the July 9 independence date.

A referendum on Abyei's future was supposed to have been held simultaneously, but the two sides could not agree on who was eligible to vote, and Abyei's referendum wasn't held. The black African tribe of the Ngok Dinka, which is allied with the south, and the Arab tribe of Misseriya, which is allied with the north, both claim the area.