(Adds French minister comments on Chavez role in paragraphs 11-12)

PARIS, March 3 (Reuters) - A rebel commander killed by Colombian forces was France's contact in negotiations aimed at winning the release of hostage Ingrid Betancourt, French Foreign Minister Bernard Kouchner said on Monday.

"It is bad news that the man we were talking to, with whom we had contacts, has been killed," Kouchner told France Inter radio. "Do you see how ugly the world is?"

Colombia's military said on Saturday its troops had killed Raul Reyes, considered by analysts to be number two in the Revolutionary Armed Forces of Colombia (FARC), dealing a severe blow to Latin America's oldest guerrilla insurgency.

The killing came days after a former FARC hostage said Betancourt had been mistreated and kept in chains, had a serious liver problem and was mentally exhausted.

Betancourt is a former Colombian presidential candidate who also holds French nationality. She has been held hostage by the FARC in the Colombian jungle for six years and her plight has become a major political issue in France.

"We need to redouble our efforts to talk about Ingrid Betancourt," Kouchner said, adding that she was a "medical emergency".

The killing, carried out beyond Colombia's border in Ecuador, infuriated both Ecuador and its ally Venezuela. Both countries have sent troops to their borders with Colombia and downgraded diplomatic ties. In Geneva, Colombian Vice-President Francisco Santos called at the U.N. Human Rights Council for international help to free the hundreds of people held by FARC guerrillas in what he said were concentration-camp like conditions.

He said all states were committed by U.N. Security Council resolution to fight terrorism and to thwart anyone using their territory to plan or commit terrorist acts in other countries.

"... let there be no misunderstanding: we shall continue to be firm in our stance against the worldwide drug problem and against terrorism," he said.

France's junior foreign minister for human rights said that Paris still considered Venezuelan President Hugo Chavez an important mediator in the hostage case.

"President Chavez has taken the initiative, he had taken initiatives earlier on that had allowed for the release of several hostages even though the situation had been blocked for some time, so we are aware of his involvement and the important role he has played," Rama Yade told a news conference in Geneva. (Reporting by Crispian Balmer and Jonathan Lynn; Editing by Keith Weir)

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