Ugandan soldiers have taken their fight against the notorious Lord's Resistance Army (LRA) into the Central African Republic (CAR), the army has confirmed.
A military commander said the operation had been going on for a month with the permission of the CAR government.
The LRA's 20-year insurgency has spilt over several borders as it fights to overthrow Uganda's government and install a Bible-based theocracy.
The rebels are infamous for carrying out mutilations, kidnappings and rapes.
Tens of thousands of people have died and many more have been made homeless as LRA fighters have marauded throughout central Africa.
'Doing the job'
Although Ugandan troops have previously fought rebels in the Democratic Republic of Congo, it is thought to be the first time Kampala has confirmed its soldiers are in the CAR.
"The offensive is going on," said army spokesman Lt Col Felix Kulayigye.
"The Central African Republic authorised us to pursue the LRA in its territory. Our boys are there and are doing the job."
He said several dozen intelligence officers were operating in CAR and eastern DR Congo.
He said Kampala believes LRA leader Joseph Kony is making to the western Darfur region in Sudan.
The Ugandan rebel group is said to have killed people in several CAR towns in recent months, forcing many others to flee.
And the town of Ezo in southern Sudan was also attacked recently by the LRA.
Earlier this month the World Food Programme said it had provided food aid to 60,000 people fleeing LRA attacks this year.
The rebel group's leaders, notorious for capturing children and using them as fighters and sex slaves, are wanted by the International Criminal Court.