Ugandan rebels have killed 23 people including 14 south Sudanese soldiers and "started war", a south Sudanese minister said on Saturday.

Information Minister Gabriel Changson Chang said Lord's Resistance Army fighters attacked Nabanga village on Wednesday.

"The LRA have started war," he told Reuters. "Southern Sudan will not be the place where they can wage this war."

Nabanga was the site of tentative meetings between Ugandan officials, fugitive LRA leader Joseph Kony and south Sudanese mediators who have hosted stop-start peace talks between the two sides in the southern capital Juba since mid-2006.

But Kony failed to turn up to sign a final deal in April to end more than two decades of war in northern Uganda that have killed tens of thousands of people and displaced 2 million more.

On Thursday, a Ugandan military spokesman said the Democratic Republic of Congo and Sudan would launch a joint offensive against the LRA if Kony failed to commit to talks.