(Recasts, adds details, quotes, previous NAIROBI)

By Francis Kwera

KAMPALA, April 22 (Reuters) - Congo, Sudan and Central African Republic must join forces to free more than 350 people kidnapped in recent weeks by Ugandan rebels, an international human rights group said on Tuesday.

Peace talks between Uganda's government and Joseph Kony, the fugitive leader of the Lord's Resistance Army, collapsed earlier this month after Kony failed to appear at a planned meeting.

Kony is wanted for war crimes by the International Criminal Court in The Hague. Its chief prosecutor said the reported abductions in south Sudan, eastern Democratic Republic of Congo and CAR underlined the urgent need to bring him to justice.

Amnesty International said the kidnappings were typical of the LRA's brutal tactics during its 22-year insurgency.

"These people -- including scores of women and children -- are likely to be used as child combatants and sex slaves, and yet none of the governments in the region have done anything to try to secure their release," it said in a statement.

"The governments of Sudan, the CAR and the DRC -- with the assistance of the U.N. -- must join forces to secure the safety and release of those kidnapped immediately and bring those responsible to justice."

HOPES DASHED

Northern Uganda's civil war killed tens of thousands of people and uprooted 2 million more. It also destabilised parts of Sudan's oil-producing south and mineral-rich eastern Congo.

Hopes of an end to one of Africa's longest conflicts were dashed when Kony failed to emerge from hiding for a peace deal signing ceremony on April 10 on the remote Sudan-Congo border.

Fearing arrest, the LRA leader had never attended nearly two years of stop-start negotiations in south Sudan's capital Juba.

He has instead stayed at camps in Congo's lawless Garamba Forest, and has always insisted the international indictment targeting him be scrapped before he would disarm.

ICC Chief Prosecutor Luis Moreno Ocampo told Reuters in an email statement that he was very concerned by the reports of more mass abductions by the rebels -- and by reports that some of those abductees were being given military training.

"These are worrying developments and provide additional urgency to executing the warrants of arrest," he said.

A U.N. report obtained by Reuters included accounts from villagers who escaped LRA captivity this month. They put the rebels' numbers at 1,200, nearly half of whom were abductees.

On Monday, the United States urged the guerrilla group to sign a final peace agreement, and it praised the Ugandan government for its patience and resolve during the Juba talks. (Additional reporting by Hereward Holland in Nairobi and Susan Cornwell in Washington; Writing by Daniel Wallis) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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