By Abdoulaye Massalatchi

Niamey - Niger President Mamadou Tandja re-appointed his government without changes on Wednesday, his first act under a new constitution that has allowed him to extend his rule over the uranium-rich Saharan nation.

The formality marked a switch to a full-blown presidential system in which cabinet members will answer to Tandja rather than a prime minister, raising fears of authoritarianism and unrest in a nation where al-Qaeda is active.

"Tandja is calling the shots and the rest of the world is going to have to get used to it," said Richard Reeve, independent political risk analyst based in London.

Tandja also scheduled elections for Oct. 20 to replace the parliament, dissolved by the leader in May to remove an obstacle to his constitutional rejig.

Critics at home and abroad say Tandja's tightened grip on power is a step back for democracy and could trigger instability in Niger, which is the scene of al-Qaeda activity and a Tuareg insurgency.

The government of Niger briefly stepped down on Tuesday to allow Tandja to pick his new team. But the prime minister and all 32 other ministers were reinstalled, according to an official communique read over state radio.

Tandja, whose presidency was to end after the completion of his second term in December, won broader powers and an extended mandate in a widely criticised referendum earlier this month.

Opposition leaders denounced the reported 90 percent vote in favour of the constitutional change as fraudulent and said the referendum was tantamount to a coup d'etat.

The United Nations, African Union, European Union, the United States and former colonial power France have all criticised Tandja's move to retain power.

Tandja has argued the people of Niger want him to stay to oversee multi-billion-dollar oil, mining and infrastructure deals which could transform the impoverished country's economy.

French state-owned energy firm Areva is building a uranium mine in the north of the country, while China National Petroleum last year signed a $5-billion oil deal with Niger.

Niger's controversial referendum was one of a string of questionable votes in West Africa this year that analysts said may incite further power grabs on an unstable continent. - Reuters