Sudanese rebels and government troops clashed on two fronts, both sides said Friday, after the US urged Sudan to agree on a demilitarised zone with South Sudan, which Khartoum accuses of backing the insurgents.

Rebels of the Sudan People's Liberation Movement-North (SPLM-N) in South Kordofan state said they "liberated" a village northeast of Kologi town on Thursday, but gave no further details.

Separately, Justice and Equality Movement (JEM) insurgents from Darfur, in Sudan's west, said they and other insurgents had Thursday defeated government forces at Tanga, in the East Jebel Marra mountains of South Darfur state.

The JEM statement gave no casualty figures but said the insurgents seized vehicles from the army.

JEM and other Darfur rebels are joined with SPLM-N in a Revolutionary Front to overthrow the Arab-dominated Khartoum regime they say is unrepresentative of the country's diversity.

Following the rebel announcements, army spokesman Sawarmi Khaled Saad appeared on state television late Friday.

He accused the rebels of attacking a village in East Jebel Marra on Thursday, sparking a battle that left 32 rebels dead. The army suffered some dead and wounded, and seized equipment, he said.

Earlier Thursday, 45 rebels died in fighting with the army after the insurgents attacked east of Kologi in South Kordofan, Saad added.

Casualty claims are difficult to verify with access to both Darfur and South Kordofan restricted.

The fighting comes after Sudan and South Sudan last Tuesday resumed African Union-led talks in Ethiopia to resolve security and other crucial issues.

Sudan and South Sudan fought along their undemarcated frontier in March and April, sparking fears of wider war and leading to a UN Security Council resolution which ordered a ceasefire and the AU talks.

In early August those negotiations led to a breakthrough deal on fees due by Juba for shipping its oil through the north's pipeline for export. But Sudan says the oil deal will not be implemented unless security issues are settled first.

Khartoum accuses the government in Juba of backing rebels in the north, a charge which analysts believe despite denials by South Sudan's government, which in turn has accused the north of backing rebels in the South.

US ambassador to the United Nations, Susan Rice, on Thursday said Sudan's refusal to accept a demilitarised zone with South Sudan risks sparking "outright conflict".

Rice said it was "equally disappointing" that Khartoum refused to implement the oil accord until all differences between the two have been settled.

South Sudan has agreed to an AU map of the demilitarised zone but Khartoum has not. Its opposition has focused on the inclusion of a disputed area south of the Bahr el-Arab/Kiir River.

The United Kingdom has backed AU and UN calls for Khartoum to accept the map, saying it has no bearing on the line of a permanent border.

South Sudan separated in July last year after a 2005 peace deal ended a 22-year civil war.