OTTAWA- A United Nations special envoy to Niger who was kidnapped by al Qaeda operatives in the impoverished West African country says he was betrayed by someone who let his captors know where he would be.

Robert Fowler, a senior Canadian diplomat, was abducted with an aide close to the Mali-Niger border in mid-December last year after they had visited a gold mine. The two men were freed in Mali on April 22.

I know somebody shopped me, Fowler told the Canadian Broadcasting Corp. The CBC ran excerpts from the interview on its website on Tuesday.

Who could it be? the CBC quoted Fowler as saying. It could be the government of Niger, could be an al Qaeda sympathizer in the U.N. office in Niger, in the U.N. office in West Africa, in the ... secretariat building in New York.

At the United Nations, spokesman Farhan Haq said We don't have any information indicating that there was a leak (of Fowler's name from the U.N. secretariat).

He told a briefing: Obviously we would appreciate from whoever it comes any information, if there is such a thing.

Niger is among the world's poorest nations despite being a leading producer and exporter of uranium. The government is battling Tuareg rebels who are fighting for autonomy in the north.

Fowler, who took up his post in 2008 to try to help settle the conflict with the Tuaregs, said President Mamadou Tandja appeared offended, annoyed (and) embarrassed by the U.N.'s decision to send an envoy.

They hated my mission, the 65-year-old told the CBC.

Fowler and his aide were traveling without security guards the day they were abducted because they were in an area the U.N. had designated as safe, he said.

Armed kidnappers stopped Fowler's vehicle, transferred the men to a truck, stuffed them under a blanket and then sat on them. Fowler said he suffered a fractured vertebra during the extremely bumpy 56-hour ride that followed.

Fowler said his captors were a group of 20 men and children, ranging in age from seven to 60. When he revealed his identity to his captors they were unsurprised, he said.

At one stage, the group demanded 20 of its members be freed from detention in Mali and other countries as a condition for releasing the hostages. Malian officials initially blamed Tuareg rebels for the abduction. (Reporting by David Ljunggren and Patrick Worsnip; editing by Rob Wilson)