The United Nations said Friday that Canadian Robert Fowler, its special envoy to Niger whose disappearance west of the capital Niamey was announced Monday, was on an official visit.

"Mr Fowler came here as part of an official UN visit but we were not aware of his trip out of town to the Samira gold mine," said Modibo Traore, head of the local office of the UN Office for the Coordination of Humanitarian Affairs.

"Mr Fowler is the UN secretary general's special representative for Niger and in that capacity he is responsible for humanitarian problems and for finding a solution to the (Tuareg) rebellion," he added.

Last Friday, the day after his arrival in Niamey, Fowler meet with Interior Minister Albade Abouba and Justice Minister Dagra Mamadou, Traore added.

Traore's statement echoed that of the spokeswoman of UN Secretary General Ban Ki-moon, who appointed Fowler -- a former ambassador to the United Nations -- last July.

"I can confirm to you that Mr Fowler, as special envoy for Niger, was on an official mission," said the spokeswoman, Marie Okabe, on Thursday at a daily press briefing at UN headquarters in New York.

She refused to say more about his disappearance or his appointment, which Ban had made without an announcement.

In revealing the disappearance and feared kidnapping of Fowler, 64, and another Canadian diplomat, Louis Guay, Niger's Communications Minister Mohamed ben Omar stated Tuesday the UN envoy was not in Niger on official business.

Officially Niamey has never called on the United Nations to mediate with Tuareg rebels, whom it normally dismisses as "bandits" and "drug traffickers".

The Tuareg, who live in the remote northern deserts of Niger, say they are fighting for autonomy and a slice of the uranium wealth that lies beneath the sands of their region.

Ben Omar said Fowler had requested an invitation from the authorities to attend Niger's 50th anniversary celebrations that held Thursday in Tillaberi, to the west of Niamey.

On Tuesday, the Restoration Forces Front (FFR), a Niger Tuareg rebel group, claimed on its website that it had kidnapped the Canadians. But a few hours later, its leader denied to AFP that his group was responsible.

Fowler and Guay, plus their driver, disappeared around 40 kilometres (25 miles) west of the capital Niamey around Tillaberi, the very region where Niger celebrated its 50th anniversary of independence Thursday.

Ben Omar said the men appeared to have disappeared after visiting Samira, a gold mining site of which Canada's Etruscan Resources is co-owner. Getting to Samira from Niamey entails crossing the Niger river by ferry.

The men's car was found on the Niamey side of the river close to the jetty for the ferry, suggesting they had been to Samira and were on their way back to the capital at the time of their disappearance, Ben Omar said.

Inside the car were three phones, a camera and a jacket.