Thousands of children have been abducted by LRA rebels

The fighting follows the reported capture by Ugandan soldiers 10 days ago of four LRA bases in southern Sudan, with the help of Sudanese forces.

The LRA was an ally of the Sudanese Government for many years - until Sudan and Uganda agreed to restore diplomatic relations three years ago.

Women fighters

In the latest incident some reports suggest that Sudanese soldiers also fled to Juba after being attacked by the LRA.

The BBC's Alfred Taban in Khartoum says the LRA appears to be angry with the Sudanese army for cooperating with Uganda, and the rebels are retaliating by attacking government-controlled villages in the area.

The LRA has been fighting Uganda's President Museveni for 16 years

Displaced villagers say the LRA is well armed, and many of its members are women fighting with their children strapped to their backs.

Uganda says the operation against the LRA in Sudan is aimed at rescuing women and children captured by the LRA for use as slave labour.

Ten Commandments

The operation also marks unprecedented collaboration between the governments of Uganda and Sudan.

The military action against the LRA follows the signing of an agreement in March, whereby Sudan authorised Uganda to pursue the rebels inside its borders.

The LRA has been fighting Ugandan President Museveni for the past 16 years in north of the country, and wants to replace the constitution with the Bible's Ten Commandments.

The LRA is said to have abducted up to 12,000 children and turning them into soldiers or, in some cases, sex slaves.