Uganda on Thursday rejected what it called "staggering" demands by the Democratic Republic of Congo for $13.5 billion dollars in reparations over a brutal 1998-2003 war.

Kampala told the International Court of Justice in The Hague that the claim by its neighbour Kinshasa over the conflict two decades ago was disproportionate and "ruinous".

"Uganda considers the DRC's unbending demands to be both unfounded and excessive in the extreme," Ugandan Attorney General William Byaruhanga told the court.

"It essentially seeks to make Uganda responsible for everything that happened in the conflict, as reflected in the staggering amounts that it claims."

The ICJ, the top court of the United Nations, ruled in 2005 that Uganda had to pay Kinshasa reparations for invading its vast central African neighbour during the war that left three million people dead.

The case is now back before the Hague-based ICJ, which must make a final ruling on the amount of compensation after the two squabbling countries failed to reach agreement through negotiation.

Byaruhanga said "nothing had changed" since the DRC revived the case "except that that the DRC reduced its demand from roughly $23.5 billion to almost $13.5 billion."

"This significant drop only confirms that the DRC's claims are rooted in tactics, not reality," he said.

"From a legal perspective the DRC's claim before you remains unfounded. From a historical perspective it's dangerously disproportionate. From an economic perspective it is ruinous," Byaruhanga said.

The DRC accused Uganda of "barbarity" in its opening remarks on Tuesday, calling on it to "fully assume its responsiblity for the injury caused".

The conflict at its height drew in some nine African countries, with Uganda and Rwanda backing rebel forces against the Kinshasa government as they jostled for control of the mineral-rich Ituri region.

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