The Sudan People's Liberation Army says it is advancing on the last government-held garrison town in southern Sudan, Juba.

Speaking on the BBC's Network Africa programme, Oyay Deng Ajak said he was speaking from a position between Torit and Juba, where the government forces were trying to halt them. Some fighting had taken place, he said.

The SPLA took another garrison town, Torit, earlier this month, prompting the government to pull out of peace talks.

"We are actually moving to Juba as I speak to you now - we are moving to Juba from multiple directions", he said.

The government has said it will recapture Torit and has sent troops and militia units to Juba to prepare an offensive.

On Monday, government forces bombed Torit, the town's bishop has said.

Bishop Paridee Taban told the BBC Focus on Africa programme that some buildings had been destroyed but he was not aware of anyone being killed.

Speaking from Nairobi he said that regular bombing from the air had been taking place "since the time that the town was taken" and his colleagues in the town had warned him not to return yet.

Gunships

Mr Ajak ridiculed the Sudanese government's claims that it would retake Torit.

He added that the government air raids against Torit were not effective against the SPLA.

The government forces students to join the army

Bishop Taban said that the air raids carried out over the last week had been both high altitude ones by Antonov aircraft and attacks by helicopter gunships.

The Sudanese army has been mobilising forces, including recently recruited militiamen, in Juba ready to attack Torit.

The government wants the SPLA to agree a ceasefire and a withdrawal from Torit before it will resume talks, according to the BBC's Alfred Taban in Khartoum.

Samson Kwaje, the representative of the SPLA in Nairobi, said that his movement had not come under any pressure internationally to withdraw from Torit.

'First step'

On Sunday, thousands of militiamen left for Juba, our Khartoum correspondent said.

But he said they were not all volunteers and many had been forcibly conscripted from schools.

He added that the militias are not well-trained and suffer high casualties in the war against the SPLA.

Asked about the peace talks, Mr Kwaje said that the SPLA delegation was still in Kenya waiting for them to resume.

Alfred Taban has reported that the Sudanese Government is talking to the United States and the regional security body Igad (the Inter-Governmental Authority on Development) about resuming the talks but is still demanding that it get Torit back and that the SPLA should implement a ceasefire during the talks.

When the Sudanese withdrew from the talks a week ago, they said they would return when Torit was back in their hands.