KHARTOUM, Sudan (AP) -- Dissident rebels kidnapped a group of African Union personnel and an American monitor in Sudan's powder keg western Darfur region, AU and U.S. officials said, but some of the hostages were later released.The abductions near Sudan's western border with Chad on Sunday came a day after two African Union troops were killed by another rebel group -- the first fatalities suffered by the pan-African body since it deployed peacekeepers to Darfur in April 2004.The rebel killings and kidnappings have been condemned by the African Union, which has described them as major violations of a shaky cease-fire deal aimed at ending the Darfur conflict that started in 2003 and has claimed the lives of more than 180,000 peopleThe Ethiopian-based AU is expected to discuss the incidents at an emergency meeting Monday.Eighteen AU members and one American were taken hostage by a faction from one of two main Darfur rebel groups, the Justice and Equality Movement, said an AU official who declined to be identified further as he was not authorized to speak to the media.It was unclear if the American was among those released, nor what his exact role was, but he may have been a monitor working with the African Union, said Elizabeth Lukasavich, a spokeswoman for USAID in the Sudanese capital, Khartoum."Some people have been released but we don't know who," Lukasavich said. "The American may have been an observer or a contractor. There are quite a lot of Americans out there working as observers with the African Union troops."Americans have also been supporting the AU mission in Darfur by providing logistics and helping fly in troops.The other hostages included AU military observers, civilian police and a Justice and Equality Movement official, according to the AU official.AU Commission Chairman Alpha Oumar Konare demanded "the immediate release of all abducted" personnel, who are being held by armed men led by rebel commander Mohammed Saleh in Tine, a town on the border with Chad, according to a statement.The culprits were a dissident faction of the rebel Justice and Equality Movement, said Konare spokesman Adam Thiam."We see it as a very serious attack on the mandate of the African troops in Sudan," Thiam said.The AU first deployed to Sudan with fewer than 500 peacekeepers, but its mission has grown to 6,200 with financial and logistical support from the EU, the United States and others.The African Union on Sunday also accused the other main Darfur rebel group, the Sudan Liberation Army, for ambushing an AU patrol a day earlier and killing two Nigerian soldiers and two Sudanese drivers attached to the team in South Darfur."The deaths [of the AU soldiers] were a sad incident and we regard them as major cease-fire violations that we condemn," said the acting head of the AU mission in Darfur, Jean-Baptiste Natama, in a telephone interview.The violence occurred in generally SLA-controlled territory with a history of previous rebel interference and attacks against African Union teams, according to a statement released by the African Union Mission in Sudan."The AMIS soldiers clearly identified their attackers as men dressed in SLA uniform and that they escaped in typical SLA vehicles into which they loaded their own casualty," the statement said. "All the evidence shows SLA direct responsibility."The AU's mission commander had protested personally to the SLA's secretary general, Mini Minawi Arkoi, over the violence, the statement added.Darfur's conflict started two years ago after rebels took up arms against government forces after what it regarded as years of state neglect.Sudanese authorities are accused of subsequently unleashing militias known as the Janjaweed against the rebels and fanning a conflict that has sparked what the U.N. has described as the world's worst humanitarian crisis.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.