Tandja is the first leader to have served a full term

It says incumbent Mamadou Tandja won 40.6% of the vote and faces a run-off with the opposition's main leader Mahamadou Issoufou, who polled 24.6%.

The second round of the vote is to be held on 4 December.

The result is likely to hinge on how backers of the now eliminated third-place candidate will vote, experts say.

The candidate, parliamentary speaker Mahamane Ousmane, has yet to indicate whom he will be supporting after losing out in the first round on 15 November.

About 48% of the more than 5.2 million eligible voters turned out in the election, which observers said went smoothly.

There were six candidates standing in the first round, which was postponed from 13 November to avoid a clash with the Muslim festival of Eid.

President Tandja, an army colonel, was widely expected to win. He beat Mr Issoufou in the run-off of the 1999 poll, after being backed by Mr Ousmane.

Widespread poverty

Mr Tandja is the first president to have made it through a full term in office since independence.

Issoufou's party holds a majority in parliament

Correspondents say he has brought a measure of economic and political stability to Niger. His military predecessor was assassinated in 1999.

However, two thirds of Niger's 11 million people live on less than a dollar a day and the country is at the bottom of the UN Human Development Index.

Last year, attention was focused on the country after London and Washington found themselves in a public disagreement over the UK's claim that Iraq tried to obtain uranium from Niger.

Niger denies the charge but the UK has not withdrawn its accusation.