Ugandan President Yoweri Museveni has revealed that his forces are actively fighting rebels in South Sudanese territory, and that the country had already lost some of its soldiers in combat.

The disclosure came after Uganda legislators had retroactively backed the deployment of Ugandan soldiers to South Sudan, on the premise that they were mainly there on peacekeeping basis and helping to evacuate Ugandan nationals.

But the Ugandan leader later said that the country's army was fighting alongside loyalist South Sudan forces.

"Only the other day, January 13, the [South Sudan army] SPLA and elements of our army had a big battle with the rebel troops about 90km from Juba where we inflicted a big defeat on them," Mr Museveni told fellow regional leaders meeting for a summit in Luanda, Angola.

"Unfortunately, many lives were lost on the side of the rebels. We also took casualties and had some dead," he said, without giving figures.

The admission by President Museveni confirms claims by Ugandan MPs that the country was actively fighting in South Sudan and had lost soldiers in the crisis that started on December 15 in the capital Juba.

READ: Ugandan troops killed in South Sudan

The Ugandan army had several times denied it was involved in any combat operations in South Sudan.

Asked about the developments, Ugandan defence minister Crispus Kiyonga deflected the question to the army spokesperson, Lt Col Paddy Ankunda, who said: "Well, the President has said it."

He added: "Details are scanty at the moment but all I can say is that our forces had a very successful battle."

The President’s remarks drew condemnation from the shadow attorney-general Abdu Katuntu.

Mr Katuntu said MPs will task the Executive to explain and account for Ugandans they may have endangered by engaging in combat.

By taking sides, he said the government had pitted Ugandans against ordinary South Sudanese.

"As Parliament, we need to take steps immediately now that we know we were lied to. We want the Executive to account for Ugandans they took in and put in harm’s way in the conflict because they got our approval fraudulently,” said Mr Katuntu.

Failed coup bid

Speaking at the International Conference on the Great Lakes Region, Mr Museveni said by Wednesday evening the government of South Sudan, with the support from [Uganda army] UPDF, had regained control of Jemeza town.

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He also accused former South Sudan vice president Riek Machar of planning and executing a failed coup. "… the question is: 'If Riek Machar did not plan a coup in Juba, then why did his supporters capture Malakal, Bor, Akobo, etc?..."

"In my opinion, if Machar had not planned a coup and it had all been mistakes on the government side, he could have done two things: withdraw to a remote area of the country to avoid attack and start talks unconditionally so as to resolve the problem quickly and not to protract it," Mr Museveni said.

According to President Museveni, the crisis is a result of power struggle and "ideological, organisational and discipline issues." He also blamed the fighting on the indiscipline of the SPLA soldiers.

The ruling SPLM party, the President said, should resolve their disagreements within the party structures, and advised that those dissatisfied should form their own party.

The conference attended by among other presidents Uhuru Kenyatta of Kenya, Paul Kagame of Rwanda and host Eduardo Dos Santos of Angola, also discussed the fighting in the Central Africa Republic and DR Congo.