A rebel group in Niger has kidnapped a former Canadian diplomat at the United Nations and three others, according to a statement on the group's website.

In a message posted to its site Tuesday, the Front des Forces de Redressement (FFR) said it had captured four people, including Robert Fowler, during a commando operation Monday in the Tillabery region north of the capital, Niamey.

Fowler, a United Nations special envoy to Niger, was travelling with Canadian Louis Guay, who works for the UN and was assisting Fowler, and their driver from Niger.

All were reported missing Monday, although only Fowler was mentioned by name in the group's statement. It's assumed that Guay and their driver are amongst the others taken hostage.

The supposed leader of FFR, Mohamed Awtchiki Kriska, has denied the website's claim.

"Recently one of my colleagues has just spoken to the head of the group and he is saying he knows nothing about any such kidnapping and is denying having anything to do with it," the Agence France-Presse news agency's Helen Vesperini told CBC News from neighbouring Nigeria.

Kriska said he did know where Fowler is being held, but didn't provide details.

There has been no independent confirmation of the FFR's statement, which indicated Fowler was well and would soon be transferred to a safe place where people would look after him. Foreign Affairs spokeswoman Lisa Monette said the government is aware of the claims.

In the statement, rebels accuse Canada of providing arms to the government of Niger, led by President Mamadou Tandja, in its fight against aboriginal populations. The statement said the hostages were taken to send a message to Canada.

Uranium at stake

Niger's insurgency has been going on for a number of years and is largely aimed at the central government, which Tuareg nomads accuse of discriminating against them and of maintaining power using profits from mineral resources.

"Niger has one of the largest deposits of uranium in the world and Robert Fowler's mandate as a special envoy for the UN in Niger was to conduct talks with these different factions," the CBC's Catherine Mercier reported from New York.

"But this being so close to the capital really sends a strong message about the strength of the insurgency in Niger."

While uranium mining in Niger used to be the preserve of France, the government of Niger 18 months ago opened up mining concessions to other countries, including Canada and China.

One of the world's least developed and poorest nations, the West African country of Niger has suffered decades of political turmoil and civil war.

The FFR is reportedly a splinter faction of a larger insurgent organization known as the Movement of Niger People for Justice, or MNJ, that has been operating in the northern part of the country for two years.

The vehicle in which Fowler and Guay were travelling was found Sunday evening in good working condition about 40 kilometres northeast of the capital, Niamey. Cellphones, a camera and jacket were reportedly found in the vehicle.

Fowler, 64, arrived in the country a few days earlier for talks with government and non-governmental officials.

There were conflicting reports as to the exact nature of his business in Niger, Vesperini said. One version suggested he was on official business for consultations with the Niger government, while another said he was in the country for a private visit.

"Officials in Niger have been quoted as saying on two previous occasions he had asked for a permit to travel to uranium mining sites. Whether this is true, I'm not sure," Vesperini said.

UN spokesperson Farhan Haq said Monday officials are not sure whether the three people were on the way to or returning from a meeting with senior government officials when they went missing.

The UN learned of the situation Sunday morning and is working with the government of Niger, Haq said.

The UN had not received any demands as of Monday night. The reason for the discrepancy between when the rebels say they kidnapped Fowler and the others, and when the UN says it learned about the situation, was not immediately clear.

UN Secretary General Ban Ki-moon has told reporters he is concerned about the disappearance.

"We are mobilizing all networks," he said Monday.

Held senior roles in Canadian government

In a news release, Foreign Affairs Minister Lawrence Cannon said he spoke with senior UN officials Monday and was monitoring the situation closely.

"I am very concerned by the situation and want to assure family and friends of the missing Canadian diplomats, and all Canadians, that we will do everything we can to resolve the situation successfully," he said.

Fowler, who was appointed as special envoy to Niger earlier this year, held senior roles in the Canadian government.

With experience in some of Africa's most notorious conflict zones, including Sudan and Rwanda, Fowler was described Monday as someone who doesn't hesitate to thrust himself into front-line situations.

With files from the Canadian Press