Populist mayor Rodrigo Duterte is headed for a resounding victory in the Philippines' presidential election, according to poll monitor data.

Duterte had an insurmountable lead of 5.84 million votes over his nearest rival, with fewer than 12 percent of the total from Monday's election to be counted, according to PPCRV, a Catholic Church-run monitor accredited by the government.

The ruling party’s candidate, Manuel "Mar" Roxas, conceded defeat as he looked set to come in far second.

"I wish you success, Mayor Duterte. Your success is the success of the Filipino people,” Roxas said.

Grace Poe, who trailed third in the race, said Duterte's lead reflected the will of the people.

"I respect the result of the election," she said. "We fought hard."

Andy Bautista, head of the polling commission, said voter turnout was estimated at 80 percent, which he said was a record in the country.

While authorities described the overall conduct of the elections as peaceful, police said at least 10 people died across the country in election day violence as gunmen attacked polling stations, ambushed vehicles and stole vote-counting machines.

READ MORE: Why the Philippine 'Punisher' could be president

The Armed Forces of the Philippines National Election Monitoring Center said in a statement that they monitored 22 election-related violent incidents.

In the worst attack, seven people were shot dead in an ambush before dawn in Rosario, a town just outside of Manila known for political violence, Chief Inspector Jonathan del Rosario, spokesman for a national police election monitoring task force, told the AFP news agency.

Another 15 people were killed in election-related violence in the run-up to the polls.

Many areas of the Philippines are dominated by feuding political families. Security forces were on high alert for the vote and citizens' groups were watching polling centres closely.

Voting extended

There were several reports of electronic voting machine hitches, and voting was extended in several districts after delays in the opening of polling centres.

Al Jazeera's Marga Ortigas, reporting from Manila, said: "The commission on elections has promised transparency but already the reliability of the automated polls are being called in to question.

"The computer system was hacked just a few weeks ago, and there are fears of widespread cheating."

The election campaign exposed widespread disgust with the Southeast Asian country's ruling elite for failing to tackle poverty and inequality despite years of robust economic growth.

Tapping into that sentiment, Duterte, mayor of the southern city of Davao, emerged as the frontrunner by brazenly defying political tradition, much as Republican presidential candidate Donald Trump has done in the US.

The mayor's single-issue campaign focused on law and order chimed with popular anxiety about corruption, crime and drug abuse, but for many his incendiary rhetoric and talk of extrajudicial killings echo the country's authoritarian past.

Duterte's lead has concerned the ruling party so much that, a few days before the poll, the outgoing President Benigno Aquino called for the four other presidential candidates in the race to unite against the mayor, for the good of the country. But none of the candidates backed down.

Al Jazeera's Wayne Hay, reporting from Duterte's homebase, Davao, said his supporters see him as an authentic man of action.

"He is very popular here. One of the reasons he is so popular is his crackdown on crime," he said. "This used to be regarded as one of the most dangerous cities in Philippines, but now it's regarded perhaps as one of the safest.

"His supporters, people who are voting for him, believe he should take a lot of credit for that."

But critics disapprove of Duterte's brash manner and question his ties to vigilante killings. They also claim the controversial mayor's election pledges are unrealistic.

OPINION: The Philippines' autocratic nostalgia

"He made some astonishing claims that in the first three to six months of office he is going to solve major problems, like crime and corruption," Richard Heydarian of De La Salle University told Al Jazeera.

"Of course no experts will agree with him."

In the hometown of former dictator Ferdinand Marcos, Batac city, support for the Marcos family is still strong.

Thirty years after the family was forced to flee Manila’s Malacanang palace, the son of the late leader, Ferdinand Marcos Jr, had been tipped to become the country's new vice president.

Ferdinand Marcos Jr came out to vote early in the morning in Batac.

"He said he is very confident about victory," Al Jazeera's Sohail Rahman, reporting from the polling station where the candidate voted, said.

But with 90 percent of votes counted, administration candidate Leni Robredo had a slight lead over Marcos.

Ferdinand Marcos Jr's 86-year-old mother, Imelda Marcos, also took part in Monday's election.

The former first lady, who famously left behind her trove of designer shoes when Marcos' family was flown out of the presidential palace on a US helicopter towards exile in Hawaii, has been serving in the congress, and in this election she is seeking to win her congressional seat once again to go back to Manila.

If she wins, this will be her third and last term in congress.

More than half of the population of 100 million people were registered to vote in the election to choose a president, vice-president, 300 politicians and about 18,000 local government officials.