Niger's opposition figure Hama Amadou was imprisoned on Monday for his alleged role in the unrest that followed the result of the presidential election following three days in detention, the public prosecution service told AFP.
Hundreds were arrested and two were killed after violence erupted following the electoral commission's declaration that the former interior minister Mohamed Bazoum won the February 23 vote with 55.75%.
Prosecutors said Amadou "was placed under arrest warrant at (the prison of) Filingué" in Niamey on "many charges", including "his complicity" in demonstrations and destruction of property.
The former prime minister is also accused of "regionalist propaganda" and "of statements likely to pit people against each other".
Interior Minister Alkache Alhada had accused Amadou of being "of being the main author" of the unrest that broke out in the capital Niamey.
Amadou was banned from contesting the election result because of a conviction for baby trafficking, a charge he says was politically motivated.
He threw his support behind the only other candidate in the run-off vote Mahamane Ousmane, who garnered 44.25 percent.
Ousmane disputed the result and said he narrowly won the election.
On Monday, the opposition Cap 20/21 coalition and its allies announced their determination to "defend" the "victory" of the opponent Mahamane Ousmane "by all legal means".
The coalition said it "demands" the "unconditional release" of those arrested, including Amadou.
Among those arrested is also the former chief of staff of the armies Moumouni Boureima, a close ally of Amadou's, accused of being one of the "leaders" of the unrest in Niamey.