Mahamadou Issoufou was freed on bail after being charged
Niger opposition leader Mahamadou Issoufou has said the corruption charges he faces are politically motivated.
He strongly criticised President Mamadou Tandja's recent moves to change the constitution to allow him to seek a third term in office.
Mr Issoufou was recently prevented from flying out of the country.
Several MPs at the former parliament which refused to change the constitution have also been charged.
After being charged and freed on bail, the Niger Party for Democracy and Socialism (PNDS) leader said:
"I explained to the investigating magistrate that the matter was not really about the misappropriation of funds but rather it was a political affair," reports the AFP news agency.
Mr Tandja's moves to remain in power aroused huge opposition domestically and from donors.
But he won a huge majority in last month's referendum on changing the constitution.
He had earlier dissolved the country's top court and parliament as he pushed through his plans to overhaul the system.
The 71-year-old was supposed to stand down in December after serving two terms in office.