"Results will only really start arriving later in the day," said election commission (Cenit) spokeswoman Valerie Andrianavalona.
"Checking the results takes time," she told AFP, adding final results would probably only be available in a week.
A Western election observer said the delay was not abnormal.
"At the moment I'm not worried. It's to be expected that there's nothing on the day after the polls," he said.
"If it takes longer than a week, then yes, I'd be concerned."
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International observers said the polls went well, despite isolated incidents of violence, with fewer organisational problems than expected.
Between 50 and 60 per cent of registered voters cast their ballot, according to the Cenit.
Analysts and observers told AFP that none of the 33 candidates would win an outright majority, and that a second round of voting is likely to be held with legislative polls on December 20.