NIAMEY, June 15 (Reuters) - Thousands of opposition supporters took to the streets on Sunday in Niger's capital Niamey to demand that authorities respect civil liberties, following the arrest of several of their number last month.
Demonstrators carried signs reading 'Down with Dictatorship' in criticism of the government of President Mahamadou Issoufou, elected in 2011 following a democratic transition after a military coup the previous year.
Organisers said some 15,000 to 20,000 people took part in the march, in the centre of the dusty riverside capital. Police put the figure at 3,500.
Political tensions have risen sharply in the former French colony ahead of elections next year.
Issoufou split acrimoniously with his ally Amadou Hama, the parliamentary speaker, in August and last month some 40 members of the opposition were arrested for alleged involvement in attacking the ruling party's headquarters and the home of a legislator.
After questioning by a judge, all but six of them were released.
"There will not be any dismantling of our political parties nor underhand manoeuvres, nor threats and intimidation," Hama told the crowd. "The government in power will not break our unity."
The rally came after authorities had forbidden at least two planned protests in recent weeks by the Alliance for the Republic, Democracy and Reconciliation in Niger (ARDR), a coalition of 15 opposition parties formed in October. The opposition is calling for the release of its six members from prison.
Niger, with a fast-growing population of 17 million people, remains one of the poorest countries in Africa despite being the world's fourth largest producer of uranium and having started pumping oil in 2011.
Crude output was running at around 16,500 barrels a day, the IMF said in September, but is expected to climb ahead of the start of exports in 2016.
Issoufou's government recently concluded a long-delayed renegotiation of a mining contract with French state-owned nuclear firm Areva, increasing the maximum royalty tax rate payable from 5 percent to 12 percent, depending on profitability. (Reporting by Abdoulaye Massalaki; Writing by Daniel Flynn; Editing by Robin Pomeroy)