Sudanese warplanes hit Southern border regions, Southern army officials said Thursday, the latest violence in weeks of clashes that have sparked international condemnation and calls for restraint.

Antonov bombers and MiG fighter jets attacked the village of Chotchare in the South's Unity state late Wednesday, but there were no immediate reports of casualties, said Southern army spokesman Philip Aguer.

South Sudan's president would cut short his visit to China due to "domestic issues", a Chinese official said Wednesday, as violence between the world's newest nation and Sudan intensified.

The curtailment of South Sudan President Salva Kiir's visit to China was confirmed by Wu Bangguo, nominally the second-ranking Chinese leader, during a meeting between the two men in Beijing.

The African Union's peace and security body met Tuesday to discuss ongoing political crises in Mali and Guinea-Bissau and the escalating conflict between Sudan and South Sudan, urging immediate end to the conflicts.

"It is important... to find fast, equitable, just and durable solutions to the conflict in Guinea-Bissau and in Mali," AU security commissioner Ramtane Lamamra said at the meeting's opening.

South Sudan's President Salva Kiir said Tuesday Khartoum had "declared war" on his country, as violence between the world's newest nation and Sudan intensified.

Kiir's comment -- in a meeting with his Chinese counterpart -- came after Sudanese warplanes bombed South Sudan's oil-rich border regions overnight, as violence persisted despite international calls for restraint.

Sudan, which has rejected a return to the negotiating table, accused South Sudan of undermining its stability by backing rebels inside its territory despite international appeals for it to stop.

The "South Sudan government did not respond to the repeated calls of the international community and continued its hostile activities to undermine the stability and security of Sudan," said the foreign ministry.

U.S. President Barack Obama said on Monday that the "killing of innocents" must end in Sudan and South Sudan, after weeks of border fighting in contested regions and tension between the two states.

"In Darfur, Abyei, South Kordofan and the Blue Nile, the killing of innocents must come to an end. The presidents of Sudan and South Sudan must have the courage to negotiate because the people of Sudan and South Sudan deserve peace," Obama said at the U.S. Holocaust Museum in Washington.

The European Union could sanction the governments of Sudan and South Sudan if they continue to attack each other, France's Cooperation Minister Henri de Raincourt said Monday.

"If matters don't evolve favorably we could consider establishing sanctions against those who don't respect the conditions for resolving the crisis," he said during EU foreign ministers' talks in Luxembourg.

Sudanese President Omar al-Bashir said Monday there will be no more talks with South Sudan, despite the urging of U.S. President Barack Obama and United Nations chief Ban Ki-moon.

"No negotiation with those people," he said of the South Sudanese regime, which he earlier described as an "insect" that must be eliminated.

Sudanese war planes on Monday launched a fresh bombing raid on Bentiu, capital of the oil-rich South Sudan border state of Unity, killing at least one child, officials said.

"This is a serious escalation, and a violation of the territory of South Sudan... I think it is a clear provocation," Mac Paul, the South's deputy director of military intelligence said.

More than 1,000 South Sudanese troops died during the battle for Sudan's main oilfield of Heglig, the Sudanese armed forces commander said on Monday, as a stench of death filled the air.

"The numbers of killed from SPLM are 1,200," Kamal Marouf said during an address to thousands of troops in the area, from which Southern forces said they had withdrawn at the weekend.