By Abdoulaye Massalaki
NIAMEY (Reuters) - Niger's President Mahamadou Issoufou is far ahead of rivals in a contentious election in which he is seeking a second term, according to early results from Sunday's vote that have already been contested by opposition leaders.
Provisional results on Thursday from 170 of the West African country's 308 communes gave Issoufou 52 percent of the vote, according to the national election authority.
Under election rules, a candidate must have 50 percent of the vote to win in the first round; otherwise, the top two candidates must compete in a run-off poll.
An opposition coalition had already vowed to block Issoufou's bid for another term by uniting behind his opponent in the second round.
Opposition leader Hama Amadou, who was jailed before Sunday's poll, received 15 percent of the vote. Seyni Oumaru, who finished second in the last election in 2011, garnered 10 percent.
The location and population size of the 170 communes were not immediately clear.
Sunday's vote, which spilled into Monday due to logistical problems, was peaceful but tense. Security forces patrolled cities and villages in case of unrest or militant attacks.
Opposition parties, who accuse Issoufou of seeking to suppress dissent and of ordering the arrest of opposition supporters in the run-up to the vote, said initial results that came out on Tuesday were fraudulent
Issoufou has dismissed the criticism as politically motivated. He has also vowed to tackle deep poverty and crush Islamist militants, notably the Nigeria-based group Boko Haram, whose violence has spilled across the border.
Niger, which produces uranium and oil, is ranked last in the U.N.'s Human Development Index.
(Writing by Edward McAllister; Editing by Makini Brice and Dominic Evans)