* Election meant to end junta rule
* Junta leader says election "a new beginning"
* Mineral riches have drawn investment plans
(Adds polls closing, counting starting)
By Abdoulaye Massalatchi
NIAMEY, Jan 31 (Reuters) - Nigeriens voted peacefully on Monday in an election meant to end a year of military rule in the West African country but the outcome could prove contentious because of fears of fraud and disorganisation.
Polls closed at 7 p.m. (1800 GMT) and counting started, with the only serious disturbance reported in Tassara in the northeast, where security sources said some polling stations were attacked.
Local radio stations and a Reuters journalist who visited polling stations estimated turnout in the capital, Niamey, at below 50 percent.
The election commission said at the weekend it had been informed fake voter identification cards were sold before the poll, without saying how many, while eight of the election's 10 candidates had called in vain for the postponement of the vote to allow time for better preparation.
"I voted, but in a spirit of doubt and disappointment," said one of the candidates, former premier Hama Amadou, after casting his ballot in the capital Niamey.
Niger, a producer of uranium, is among the world's poorest countries and is facing a growing threat from al Qaeda-linked militants operating in its northern desert region, but its minerals riches have attracted billions of dollars in planned investments.
A smooth election is seen as important for countering the rising regional security threat and ensuring minerals investments benefit the country's 15 million people.
The junta took control in February 2010 after removing President Mamadou Tandja, who had tried to extend his time in power, and has won international plaudits for vowing to step down by April.
Some political leaders called for the poll to be delayed after they said municipal elections held earlier this month were flawed. Junta leader General Salou Djobo rejected their complaints, a decision analysts say could undermine Monday's election.
"At home, the speed with which the ruling junta has sought to end its military government is not universally regarded as a virtue," said Nana Ampofo, partner at Songhai Advisory LLP.
"For some the poorly organised local elections of 11 January appeared to confirm fears of unreadiness which, if repeated at the presidential and legislative level, could rob the incoming government of legitimacy," he said.
Officials reported some cases of delays to opening voting stations on Monday because of shortages of materials, similar to problems during the local elections. Results are due within three days.
Djibo said on Monday the election marked a new era.
"It gives me a feeling of real satisfaction and hope," he said after voting amid heavy security. "Hope because it is a new beginning for Niger, a departure that will allow new leaders to focus on development."
Among the candidates seeking the presidency were veteran opposition leader Mahamadou Issoufou and two former prime ministers, Seini Oumarou of Tandja's MNSD party and Hama Amadou. Parliamentary elections are being held simultaneously.
Six candidates including Oumarou announced a coalition seen bolstering the MNSD's chances and which was immediately attacked by rivals as a step back to the Tandja era.
Tassara, where the trouble was reported, is a stronghold of Issoufou's but it was not clear if the credibility of the vote was at risk.
West African regional bloc ECOWAS has sent hundreds of observers. The European Union has also sent observers, although they have not been deployed in the north of the country after a series of kidnappings by al Qaeda's north African wing.
French nuclear firm Areva is the country's biggest uranium player, although Chinese, Canadian and Australian firms are also planning investments in minerals. (Writing by Richard Valdmanis; Editing by Andrew Dobbie)