Police said some 2,000 opposition supporters took part in the protest in Niger's capital Niamey on Saturday, calling for an end to perceived government corruption, media censorship and worsening food security in one of the world's poorest nations.
The alliance of opposition parties who organized the protest put attendance closer to 30,000, according to news agency Reuters.
Demonstrators gathered outside parliament chanted "Down with the regime!" and "No to dictatorship" in the largest show of unrest since pro-democracy demonstrations triggered the military coup which ousted former president President Mamadou Tandja, in February 2010.
Saturday's rally was also first major street demonstration since
"Mahamadou Issoufou promised an end to food insecurity but the population continues to be decimated by hunger and thirst," said opposition leader Amadou Hama.
Meanwhile Leader of opposition party, the National Movement for the Development of Society (MNSD), and former premier Seini Oumarou condemned "the bad governance and corruption" under the president.
He also criticized the ruling Nigerien Party for Democracy and Socialism's control of the media and its oil deals with foreign firms.
"We are witnessing the organized looting of our national resources," he said at an opposition meeting after the rally.
The organizing coalition - the Alliance for the Republic, Democracy and Reconciliation in Niger (ARDR) - was formed from 15 opposition parties in October in response Issoufou's creation of a national unity government.
Hama and Oumarou are considered the main challengers to the president, who is widely expected to run for a second term in 2016.
ccp/jr (AFP, Reuters)