The eleven French presidential election candidates take part in a special political TV show entitled "15mn to convince" at the studios of French television channel France 2 in Saint-Cloud, west of Paris, on April 20, 2017. (AFP PHOTO/Martin BUREAU)

PARIS, April 22 (Xinhua) -- Millions of French voters will go to the polls on Sunday for the first round of presidential election, the country's most unpredictable contest likely to shake France's traditional political landscape.

Anti-establishment sentiment coupled with public disenchantment over economic malaise and security concerns has been highlighted throughout the election campaigns.

Days before voting begins, the presidency race tightened with opinion polls made neck-and-neck four main players, centrist Emmanuel Macron, far-rightist Marine Le Pen, conservative Francois Fillon and far-left candidate Jean-Luc Melenchon.

In a survey released on Friday by research firm Odoxa, the first one conducted after Thursday night's attack on police officers in the Champs-Elysees avenue in Paris, 24.5 percent of the respondents said they would vote for Macron, down by half a point from a previous survey.

Le Pen improved her score by one percentage point to 23 percent "after an almost-continuous period of decline during many weeks," Odoxa's director Gael Sliman said.

Fillon and Melenchon were both 19 percent, down 0.5 percentage points, the survey indicated.

The poll showed that Thursday's shooting incident has benefited only the far-right candidate, while having only a marginal but rather bearish effect for each of the other three candidates.

Other polls in the past few days had indicated similar results, in which Macron will face off Le Pen in the second round of votes on May 7, and win by majority.

However, analysts said all scenarios are expected for Sunday.

"It's an election of surprises with four candidates who might go through to the second round," Guillaume Indigo, an analyst at BVA pollster, said.

"No one is able to say who will be the winner as many things could happen at last minutes," he told Xinhua in a recent interview.

With a third of 45.7 million voters are still undecided, an expected high abstention rate may inject further uncertainty into Sunday's voting, which according to Indigo "may determine the election's results."

In 2012, the turnout was 79.5 percent in the first round. This year it is expected to be between 72 percent and 77 percent, BVA data showed.

A weak turnout could favor conservative ex-prime minister Fillon, as his supporters, majority of them being senior and retired voters, "are the most mobilized," and the most sure of their choice.

On the contrary, a low abstention could benefit Le Pen and Melenchon if a large number of workers and young voters cast their ballots, according to the analyst.

TIGHT SECURITY

Following Tuesday's arrest in Marseille of two men suspected of plotting an attack during the election period, and Thursday's shooting that left one police officer dead and two others severely injured, French authorities have vowed to mobilize "all right means" to safeguard the election.

French President Francois Hollande pledged on late Thursday "absolutely vigilant" security measures for the election.

Interior Minister Matthias Fekl said 50,000 police, gendarmes and soldiers would be deployed during the election to guarantee security in 67,000 polling stations across the country.

"Everything has been put in place to ensure the security of this big event for our democracy and our republic. The security forces are mobilized everywhere across France to ensure the security of French people and to ensure the presidential campaign goes smoothly," Fekl said.

Media reports said that the four main presidential candidates had all been warned of the risk of an eventual attack.

"No threat can be ruled out. The menace is permanent and of a high-level," Fekl said in a recent interview.

The extremist group Islamic States has claimed responsibility for Thursday's shooting.

The French police are still investigating into whether the assailant had accomplices, Paris prosecutor Francois Molins told reporters on Friday.

France has already imposed a state of emergency to empower police after the Paris attacks in November 2015, which killed 130 people.