The African Union will launch a 5,000-strong military force on Saturday in Juba, Southern Sudan, to hunt down fugitive warlord Joseph Kony, whose global profile shot up recently thanks to a celebrity-backed Internet campaign to bring him to justice.

The force, which Uganda said it would lead last week and the AU authorised on Friday, brings together soldiers from South Sudan, the Democratic Republic of Congo and Central African Republic, as well as Uganda.

It will be based in the South Sudan city of Yambio, close to the border with the Democratic Republic of Congo, the AU's Special Envoy for the (Kony's) Lord's Resistance Army (LRA) Francisco Madeira told reporters in Entebbe, after a meeting which brought together AU, United Nations and Ugandan officials.

Madeira said the force would be deployed in jungle areas where Kony and his fighters are known to be at work.

Asked how long the force would be operating, Madeira said: When we capture Kony or he hands himself in or we neutralise him in some way, that will be the end. That's the timeframe.

A hundred U.S. military advisers deployed to Uganda were already helping to capture Kony, but the task force needed more international support, Uganda's defence minister said last week.

Kony, accused of terrorising northern Uganda for two decades, is wanted by the International Criminal court for war crimes. He is accused of abducting children to use as fighters and sex slaves and is said to like hacking off limbs.

Violence has subsided since 2005 when the LRA was ejected from Uganda and now Kony is believed to command only hundreds of followers, scattered in jungle hideouts.

A video about Kony posted on YouTube by a California film-maker has been viewed by tens of millions of people, promoted on Twitter with the hashtag #Kony2012 and endorsed by major Hollywood celebrities.

(Reporting by Elias Biryabarema; Writing by Yara Bayoumy; Editing by Louise Ireland)