By Alain Iloniaina
ANTANANARIVO (Reuters) - Madagascar's first presidential election since a coup in 2009 will go to a run-off due in December after no candidate won an outright majority in last month's first round vote, provisional results showed on Friday.
The head-to-head contest risks escalating political tensions on the Indian Ocean island mined for its nickel and cobalt, pitting two aspirants backed by Madagascar's biggest political rivals against each other.
European and southern African observers have said voting had been free and fair, a boost for Madagascar, which needs a credible election to rebuild investor confidence and win back suspended aid.
By 1300 GMT Friday, two weeks after polling day, results from voting stations accounting for 99.9 percent of registered voters had been validated by the electoral commission (CENIT).
The provisional numbers were shown on the CENIT website www.cenit-madagascar.mg
They showed Hery Rajaonarimampianina, backed by coup-leader-turned-president Andry Rajoelina, with 15.9 percent of valid votes and Jean Louis Robinson, supported by Marc Ravalomanana, who Rajoelina ousted, with 21.1 percent.
"This is an election between Rajoelina and Ravalomanana," said Toronto-based Mark Sorbara of Africa Risk Consulting. "Therefore the underpinnings of the politically and personally tense relationship between the two is still at play."
Although they gave a nod to the overall voting process, European observers raised concerns over glitches in the registration of voters which left large numbers unable to cast ballots and opaque campaign fundraising.
Diplomats caution the electoral process could still be derailed. They are watching carefully the military, parts of which they remain opposed to the return from exile of Ravalomanana - a scenario widely expected if Robinson wins.
Under the CENIT's own timeline, it should announce complete provisional results by the end of Friday, which then go to the Special Electoral Court (CES) for validation.
"We know the election wasn't perfect," said Hanitra Razafimanantsoa, a close political ally of Ravalomanana and Robinson.
"But at this point, we accept the results," she said, speaking to Reuters when more than 90 percent of votes were in.
Rajaonarimampianina's camp echoed similar sentiments.
(Additional reporting and writing by Richard Lough in Nairobi; Editing by Angus MacSwan)