Niger's President, Mamadou Tandja, has dissolved the uranium-rich country's parliament a day after his bid for a third term in office was ruled illegal.

He assumed executive powers after the constitutional court turned down his attempt to extend his time in power.

The court had found it would be illegal for Mr Tandja to hold a referendum on a change in the law, to allow him to continue as head of state.

Opponents have said they fear a return to dictatorship if Mr Tandja stays on.

"By virtue of a presidential decree, the National Assembly is dissolved," state radio said, reported AFP news agency.

President Tandja is due to complete the permitted maximum of a decade in power later this year.

Widespread opposition

He has insisted the people of Niger want him to stay beyond the end of his second five-year term.

But his plans to remain in office have been met with widespread opposition by political and civil groups.

The constitutional court said Mr Tandja, 70, was breaking his oath of office by trying to hang on.

"The president... cannot seek the amendment of the constitution without violating his oath," the court said in a statement on Monday.

Mr Tandja was first elected in 1999, and then again five years later.

He had previously promised to quit in December this year, a month after presidential elections are due to be held.