Uganda's president says his troops have joined forces with the South Sudanese military and are fighting in Bor to end a rebellion in the world's newest country.

Lieutenant Colonel Paddy Ankunda, the military spokesman, said on Thursday that Ugandan forces were helping loyalist forces flush rebels out of Bor, the strategic town near the capital of Juba that has seen some of the fiercest clashes since violence broke out in South Sudan in mid-December.

Ugandan officials have previously denied that their troops have joined the fight, saying their forces were deployed in South Sudan mainly to aid civilian evacuations.

The involvement of a foreign army in South Sudan's conflict could escalate a crisis set off by a power struggle between President Salva Kiir and Riek Machar, the fugitive former deputy president who commands rebel forces.

It comes a day after Uganda's president, Yoweri Museveni, admitted for the first time to helping his South Sudanese counterpart fend off the rebellion.

Uganda's troop involvement in combat in South Sudan could raise concerns that other regional countries could be sucked into the conflict, fighting their own proxy wars as has happened elsewhere on the continent, such as Congo.

A spokesman for the prime minister of Ethiopia, where peace talks are taking place, said earlier this month having Ugandan troops engaged in combat would be "absolutely unwarranted".

"Only the other day, Jan. 13, the SPLA and elements of our army had a big battle with these rebel troops at a point about 90km from Juba," Museveni said. 

"We inflicted a big defeat on them. Unfortunately, many lives were lost on the side of the rebels. We also took casualties and also had some dead."

Kuol Manyang, South Sudan's defence minister, said the Ugandan forces in his country numbered "a battalion", and that
they were there to help quell the rebellion by Machar.

Source: AFP