Robert Fowler, former Canadian ambassador in Italy and now a UN special envoy to Niger, was travelling in the West African nation of Niger with another Canadian diplomat and a driver when they were abducted last Dec. 14. (University of Ottawa)

The UN secretary general called again for kidnappers to free two Canadian diplomats abducted late last year in Niger, following the weekend release of their driver in neighbouring Mali.

Ban Ki-moon issued a statement through his spokesman Monday, calling for the release of Robert Fowler and Louis Guay and praising the co-operation of local governments and individuals who helped Soumana Mounkaila gain his freedom on Saturday.

"The secretary general renews his call on those holding Robert Fowler and Louis Guay to release them both without any further delay," Ki-moon's spokesperson said.

Fowler — a UN special envoy to Niger who previously served as Canadian ambassador in Italy, and his assistant, Guay, were travelling in Niger last Dec. 14 when they were abducted. Their vehicle was found abandoned that day in good working condition about 40 kilometres northeast of Niger's capital, Niamey.

Foreign Affairs spokesperson Lisa Monette called Mounkaila's release "wonderful news." But she said officials were concerned for the lives of the two Canadian diplomats.

"Our officials continue to work both urgently and closely with our partners to secure the release of Mr. Fowler and Mr. Guay," she said.

Last month, an al-Qaeda North African group claimed responsibility the kidnappings. The group, known by the French acronym AQMI, also said it was holding four European tourists taken in January. AQMI said at the time all six were abducted in Niger and issued the alleged names of the tourists.

But Niger's president, Mamadou Tandja, has blamed the Canadian diplomats' abduction on a rebel group from the northern Niger ethnic minority of Tuareg nomads who are battling the government.

Tuareg rebels from the Front For Forces of Redress retracted an initial statement claiming responsibility for the kidnapping, saying their website had been hacked.

But some western intelligence officials believe the Tuaregs may have traded the hostages to al-Qaeda.

With files from the Associated Press, the Canadian Press