The United Nations Security Council has called for an immediate end to fighting between Sudan and South Sudan.

U.S. Ambassador to the U.N. Susan Rice said U.N. officials briefed the Security Council Tuesday, noting that the withdrawal of South Sudanese troops from the oil town of Heglig was initially encouraging, but has resulted in increased bombings by Sudan.

“Council members welcome the withdrawal from Heglig by the SPLA, demanded an immediate halt to aerial bombardments by the Sudanese Armed Forces and urged an immediate cease-fire and a return to the negotiating table.”

Rice said the U.N. Mission in South Sudan confirmed the bombings in Unity state killed at least 16 civilians and injured 34 others.

The African Union on Tuesday gave the two countries 90 days to settle their disputes over oil, citizenship and boundary issues or face binding international arbitration.

South Sudan's deputy defense minister, Majak D'Agoot, told VOA the next few days will be “crucial” to avoiding an all-out war.

During a visit Tuesday to China for talks with Chinese President Hu Jintao, South Sudanese President Salva Kiir said Sudan's bombings of southern territory amount to a declaration of war against his country.

The Chinese leader called for restraint from the two Sudans. Chinese state television later reported that Mr. Hu expressed hope that both Sudans will cease conflicts along their border and settle their issues through peaceful negotiations.

The White House Tuesday condemned Sudan's military incursions into South Sudan. White House spokesman Jay Carney said the United States calls on both governments to agree to an immediate cease-fire and recommit to negotiations.

South Sudan's military has been sending reinforcements to the border with Sudan. Military officials said they were preparing defensive positions to respond to any further provocation from Khartoum.

Sudan and South Sudan have been on the edge of full-scale war after the SPLA withdrew from Heglig, which they occupied for 10 days earlier this month.

Juba claims they left the area in response to international pressure, while Khartoum claims it retook control by force.

Sudan's president, Omar al-Bashir, visited Heglig Monday to demonstrate that the territory was under his forces' control.

Sudan and South Sudan previously fought a 21-year civil war that killed more than 2 million people. The war ended with a 2005 peace agreement that included an independence referendum for the south.