KHARTOUM - Sudan told UN chief Ban Ki-moon on Saturday that it had no choice but to fight back against “aggression” from South Sudan. Foreign Minister Ali Karti made the remarks when Ban telephoned him, the foreign ministry said in a statement. Ban asked Sudan to show restraint, the ministry said, but Karti replied that Sudan could not wait and had acted militarily “to push out the aggressor from its land.” The South Sudanese army claimed to still be in control of the Heglig oil centre, along the disputed border, after Khartoum said it had launched an offensive to recapture the area which Southern troops took control of Tuesday.

World powers have urged restraint after the latest round of heavy fighting began with waves of aerial bombardment against the South.

The leaders of both countries have accused each other of wanting war.

On Saturday a Sudanese air strike on Bentiu, capital of South Sudan’s oil-rich border state of Unity, left five people dead and six others wounded, state government spokesman Gideon Gatfan said.

The UN Security Council on Thursday demanded a “complete, immediate and unconditional end to all fighting... aerial bombardments... cross-border violence.”

It also urged the Sudan People’s Liberation Army of South Sudan to withdraw from Heglig and called on the two countries’ leaders to meet “immediately,” after April 3 talks were canceled.

The clashes are the worst since South Sudan won independence in July after one of Africa’s longest civil wars, and have raised fears of a return to full-scale conflict.