Mamadou Tandja says the people of Niger want him to stay in power
An opposition leader in Niger has accused the president of carrying out a "coup d'etat", by dissolving the country's highest court.
Bazoum Mohamed of the PNDS party told the BBC that President Mamadou Tandja did not have the right to scrap the court and suspend the constitution.
The court has three times ruled against the president's plan to change the law to let him seek a third term in office.
On Friday, Mr Tandja, 71, announced he would rule the country by decree.
His plans to remain in power have sparked domestic protests and been criticised by international donors.
Meanwhile, prominent human rights campaigner Marou Amadou was arrested on Monday night and accused of sedition, calling for a military uprising and demoralisation of the army.
The opposition is calling for a general strike, or "Operation dead city", on Wednesday to oppose the president's plan.
They are also calling for nationwide protests on Saturday to call on him to resign.
Despite the opposition of parliament and the courts, President Tandja has scheduled a referendum for 4 August on changing the constitution to let him seek a third term in office.
He has already dissolved parliament - new elections are due on 20 August.
Mr Tandja has governed the West African nation since 1999, serving two terms. He is due to step down in December.
But supporters of Mr Tandja say he has brought economic growth to one of the world's poorest nations and so deserves the right to seek re-election.