Ex-rebel wins Aceh polls

"I'm certain there will not be a second round because it's a win by a large amount," said Denny Januar Ali of LSI (Indonesia Survey Institute).

Ali said Yusuf had received 39 percent of the vote.

LSI researcher Widdy said the result was a surprise as Yusuf and his running mate Muhammad Nazar won in almost every district of Aceh, while previous research had indicated they would only have strong support in former rebel strongholds.

"This is a major project for us to study. Why was this pair elected?" he said.

Muhammad Jafar, head of Aceh's independent election commission, said a candidate needed 25 percent plus one vote to win outright without going to a second round.

The quick count was based on a sample of voting stations.

Yusuf is the leader of the "young Turks" within the former separatist Free Aceh Movement (GAM) and enjoys support from former combatants.

In 2003, he was sentenced to seven years for rebellion and had his sentence increased to nine years on appeal. He escaped when the tsunami struck on December 26, 2004 and flooded his prison.