Tunisian secularist leader Beji Caid Essebsi has beat incumbent President Moncef Marzouki in the first round of the country's landmark presidential election, but the two men will now have to stand again in a December run-off, early results show.

Essebsi, from the Nidaa Tounes party, received 39.46 percent in Sunday's poll, short of the overall majority needed but ahead of Marzouki, who got 33.4 percent, according to the latest figures.

Essebsi, 87, served as an official under toppled ruler Zine el-Abidine Ben Ali, while Marzouki, 69, is popular amongst Islamists.

With just six percent separating the two candidates, who represent very divergent views of Tunisia's future, the run-off in two weeks time looks likely to be a tight race, and both sides have already started campaigning.

Al Jazeera's Omar Al Saleh, reporting from Tunis, said all the candidates who took part in the first round have now been given three days to file any appeals.

"The election commission will look into the appeals. If the election commission does not receive any complaints then they will have to decide between two dates to hold the second round, either December 14 or December 21," he said.

"In case they receive any complaints by any candidates regardless of how minor they are, then the second round will be held on the December 28."

The head of the EU observer mission said on Tuesday that Tunisia's first presidential election since the 2011 revolution had been credible and transparent.

"On Sunday, the Tunisian people renewed their commitment to democracy ... in pluralist and transparent elections," Annemie Neyts-Uytterbroeck said.

"The exercise of freedom of expression and assembly was guaranteed," she said, describing most of the observed irregularities as "minor".

Al Jazeera's Mohamed al-Bakkali, reporting from Tunis, said the battle will be polarised. 

"The difference between the two candidates is very small, unlike what opinion poll had earlier predicted," Bakkali said.

Candidate Hamma Hammami, the leader of Tunisia's Popular Front, came in third with seven percent of the votes.

More than three years since overthrowing Ben Ali's one-party rule, Tunisia has been able to adopt a new constitution, and rival secularists and Islamist parties have largely avoided the turmoil that has plagued other Arab states swept by popular revolts.

The Islamist Ennahda Party did not field or endorse a candidate in the presidential elections, but its supporters are believed to be backing Marzouki.

Source: Al Jazeera and agencies