Warring generals in Sudan have agreed "in principle" to a seven-day ceasefire, the government of neighbouring South Sudan said Tuesday, after regional envoys denounced repeated violations of previous truces.

Diplomatic efforts have intensified to end more than two weeks of war in Africa's third-largest country as warnings multiply about a "catastrophic" humanitarian crisis.

More than 430,000 people have already been forced to flee their homes, the United Nations said.

Hundreds of others have been killed and thousands wounded.

Sudan's army chief Abdel Fattah al-Burhan and his deputy turned rival, Mohamed Hamdan Daglo, who commands the paramilitary Rapid Support Forces (RSF), "have agreed in principle for a seven-day truce from May 4th to 11th," the South Sudanese foreign ministry in Juba said in a statement.

Multiple truces agreed since fighting began on April 15 have been repeatedly violated, including one announced by South Sudan early in the war.

Witnesses reported renewed air strikes and anti-aircraft fire in Khartoum on Tuesday.

The repeated violations sparked criticism earlier Tuesday at a meeting in Addis Ababa, Ethiopia, of the Extended Mechanism on the Sudan Crisis which brought together African, Arab, UN and other representatives.

The UN refugee agency said more than 100,000 people were estimated to have fled to Sudan's neighbours.

But some relief has been arriving in the country.

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