CONAKRY (Reuters) - The United Nations on Sunday called upon Guinea's electoral commission to publish results of a September 28 election aimed at completing a transition to democracy, saying it was concerned over the delay.

Disputes over a published partial count have held up the final result and raised fears of a resurgence of violence that killed about 50 people before the vote.

The opposition is calling for the election to be annulled, dampening hopes for an end to years of instability since a 2008 military coup that deterred investment in the world's largest bauxite exporter.

The United Nations and representatives of donor nations that brokered a deal with the opposition to end protests and allow the legislative vote said they were concerned by delays in the publication of the results.

"(Guinea's) National Election Commission should make every effort to complete the tabulation of preliminary election results for publication in any event before Eid al-Adha (the Muslim feast on Tuesday)," the U.N. said in a statement.

It called upon political parties and the election commission to co-operate in publishing results from the Matoto district in the capital, one of the country's biggest, which both sides claim to have won.

Partial results to date show President Alpha Conde's ruling RPG party with a slight lead over opposition leader Cellou Dalein Diallo's UFDG and former prime minister Sidya Toure's UFR.

Opposition groups have rejected those results and last week pulled their representatives out of the election's organizing commission, calling for the vote to be annulled.

(Reporting by Saliou Samb; writing by Bate Felix; editing by Tom Pfeiffer)