NIAMEY, June 14 (Reuters) - Tens of thousands of people marched through Niger's capital Niamey on Sunday to protest against President Mamadou Tandja's plans to hold a constitutional referendum aimed at extending his rule.
Tandja is due to step down when his second term in office ends later this year but has called for an Aug. 4 referendum which could hand him another three years running the nation that soon hopes to become the world's No. 2 uranium exporter.
The rally was interrupted by the death of veteran politician Amadou Moumouni Djermakoye, who had served as foreign minister several times and was a member of the ruling majority, but who had joined protests against Tandja's plans.
Djermakoye, president of the Nigerien Alliance for Democracy and Progress (ANDP), part of the ruling coalition, was taken ill in the intense heat and died later in hospital. He was known to have been suffering from a heart condition.
The West African country's constitutional court on Friday annulled a presidential decree calling for the referendum, saying it was illegal, but opposition leaders decided to go ahead with their protest.
"The court's decision is a victory but we should not lower our guard," said Mahamadou Issoufou, head of the opposition Nigerien Party for Democracy and Socialism (PNDS), which has been spearheading the campaign against the referendum.
"With the court ruling, any order given to go ahead with the referendum will be illegal. President Tandja must submit to this," Issoufou said in a speech to the crowd, speaking before Djermakoye's death was announced.
Two lawyers interviewed on state television late on Saturday criticised the ruling by the constitutional court and questioned its validity.
"This is a difficult situation because the court's decision in our view constitutes a threat to the continuity of the state," said lawyer Djibrilou Souley.
Tandja's plans have sparked protests and drawn criticism from foreign donors and regional bodies, which said they were a step backwards and threatened sanctions against Niger.
The president says he needs the time to introduce a fully-presidential system of government that will give the presidency more power and end current blockages in governance.
He also says people want him to complete large infrastructure projects, including a hydro-electric dam, an oil refinery and French energy giant Areva's CEPFi.PA 1.2 billion euro ($1.70 billion) Imouraren uranium mine.
The United States, however, has strongly warned against the plan, saying it would be a set-back for democracy, while West Africa's ECOWAS regional political body has threatened to impose economic sanctions if Niger behaves undemocratically. (For full Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ ) (Writing by Nick Tattersall; Editing by Janet Lawrence)