By Simon Akam and Pascal Fletcher

FREETOWN (Reuters) - Sierra Leone's elections were generally well conducted, saw a large turnout, and will help consolidate democracy in the West African state if the eventual results are accepted peacefully by the contenders, European and U.S. observers said on Monday.

While praising Saturday's voting as largely calm and peaceful, the 100-strong European Union observer mission said however it noted "some shortcomings", including an "unequal playing field" during pre-election campaigning that favored the ruling party of President Ernest Bai Koroma.

Votes were still being tallied from the presidential and parliamentary polls, the third national vote held since 1991-2002 civil war that earned the country international notoriety as a "blood diamonds" battleground for rebels and child soldiers.

After a decade of recovery from the conflict, Sierra Leone's leaders and aid donors hope that new iron ore mining projects and oil discoveries can propel the war-scarred country - still one of the poorest in the world - into a new era of growth with increased prosperity for its 5.5 million people.

Since polls closed, feverish expectation has gripped the steamy coastal capital Freetown. In homes, offices and roadside markets, citizens were keeping portable radios glued to their ears as they listened to partial results from polling stations.

Electoral officials said full results could be announced either as early as Tuesday or on Wednesday.

Many predict a close-fought contest between Koroma and his ruling All People's Congress (APC) and main challenger Julius Maada Bio, a former junta leader who represents the Sierra Leone People's Party (SLPP).

"We describe this election as being well-conducted ... a contribution to democratic consolidation," EU chief observer Richard Howitt told a news conference in Freetown.

A smaller observer mission from the Atlanta-based Carter Center gave a similar assessment.

"The process was conducted with a high degree of transparency ... I was extremely impressed," the Carter Center's mission chief, former Zambian President Rupiah Banda, told reporters. He too cited "limited shortcomings".

OPPOSITION COMPLAINTS

The EU mission said it believed Sierra Leone's National Electoral Commission (NEC) was behaving with independence and impartiality and that the integrity of the election process so far was being protected.

To win outright, a candidate must gain 55 percent of the vote and the race may well go to a second round. With rivalry between the APC and the SLPP running high, there are concerns a close result could ignite violence.

"If the election continues to be well conducted and if there continues to be integrity, I hope there will be peaceful acceptance of the results," Howitt said, adding that this was the message he had conveyed to the main party leaders.

The vote is expected to be close. Former insurance executive Koroma, 59, who wrested the presidency from the SLPP in a disputed 2007 vote, is considered the narrow favorite above Bio, a 48-year-old retired army brigadier who was involved in two military takeovers in the turbulent 1990s.

Bio said in a statement his party had detected vote "irregularities" in Freetown and elsewhere, including "evidence of blatant ballot-stuffing".

The EU's Howitt cited a "low number" of irregularities reported so far. He said all complaints would be investigated.

Voters were eagerly awaiting the results. "We need a good, development-minded government," Jeremiah Komba Jimissa, 27, who runs the IT network at a Freetown hotel, said.

"We've come 10 years from the war, we're not going to go back," Jimissa, added, reflecting a repeatedly expressed view among Sierra Leoneans that they above all did not want the country to slide back into conflict.

Although ethnic allegiances still shape Sierra Leone's electoral landscape - Koroma's APC draws support from the Temne and Limba peoples of the north, while the Mende of the south and east traditionally vote SLPP - both candidates face pressure to convert the mineral riches into jobs and improved livelihoods.

Iron ore shipments by British companies African Minerals and London Mining are expected to buoy the economy to 20 percent growth this year - below original forecasts of more than 50 percent but still one of the highest growth rates on the planet.

(Writing by Pascal Fletcher; Editing by Alison Williams)