NIAMEY: Niger's President Mamadou Tandja was Friday handed a mandate to extend his rule, potentially for life, after a referendum to amend the constitution of the uranium-rich west African nation.

The national electoral commission said Tandja had won 92.5 percent of the controversial vote. Commission chief Moumouni Hamidou said turnout was officially pegged at 68.26 percent and drew some 4.1 million voters.

Tandja, 71, has consistently claimed that his bid to cling to power is to fulfil "the will of the people."

The referendum will allow the president, in power since 1999, to remain in office beyond the December 22 end of his tenure, and thereafter seek limitless mandates.

It also beefs up the president's powers by making him the "sole holder of executive power." The president will head the army, name the prime minister and have complete control over the cabinet.

Tandja had won accolades for bringing stability to Niger and improving the state of the economy of the world's third largest uranium producer but his plan to extend his mandate indefinitely was widely slammed both at home and abroad.

A 1999 constitution had limited presidential mandates to two terms.

The veteran soldier crowed victory on Thursday. Giant posters were put up in the capital Niamey reading: "For your fresh show of confidence, all of you, Thank You," and were signed by Tandja.

The opposition had called for a boycott of Tuesday's referendum, while France, the former colonial power, condemned Tandja's "repeated attacks on democracy" and the international community at large tried to persuade him to call off the poll.

The European Union has threated Niger with economic sanctions. And the Economic Community of West African States regional bloc, which Tandja once headed, has threatened similar measures.

West African powerhouse Nigeria has also voiced rare criticism of its neighbour.

"While I send my good wishes to my brother, President Tandja, I must express our deep concern about the political situation in Niger with respect to the self-succession plan," President Umaru Yar'Adua said on Tuesday.

"Nigeria and Niger are brother nations with very special ties and whatever affects one affects the other. That is why anything that can lead to crisis in Niger Republic is not something we can shy away from," he said.

The Coordination of Democratic Forces for the Republic (CFDR) -- an umbrella grouping of Niger opposition parties and unions -- has said the vote attracted only a "less that five percent participation rate."

"The CFDR reaffirms strongly and with determination that the August 4 referendum organised in breach of the laws of the republic is rejected by the sovereign people and it is null and void," it said in a statement broadcast on private radio stations.

It said the "true results have been manipulated by supporters of Tandja by seriously inflating the participation figure and giving 'Yes' voices to "phantom voters".

Tandja ran into stiff opposition from both parliament and the constitutional court in his bid to extend his rule. He dissolved both, declared an emergency and has begun to rule by decree, also appointing a new constitutional court.

The opposition, which has denounced the vote as Tandja's "coup d'Etat," had called for a boycott of the exercise.

The new measures are due to come into force within eight days of the announcement of the results by the constitutional court.