MANILA, Philippines (AP) — Thousands of protesters marked Thursday's anniversary of the 1972 declaration of martial law by late Philippine dictator Ferdinand Marcos with an outcry against what they say are the current president's authoritarian tendencies and his bloody crackdown on illegal drugs.

Hundreds of riot police were deployed to secure the marches and rallies, among the largest against President Rodrigo Duterte since he took power last year, although a new survey by the Washington-based Pew Research Center showed the president and his anti-drug campaign are widely popular in the Philippines.

Pro-Duterte followers also staged rallies in Manila. The rival demonstrations reflected deepening divisions sparked largely by the president's brutal anti-crime style.

Duterte warned he will use force or expand nationwide his declaration of martial law in the country's south if the anti-government protesters threatened public order. In May, he placed the southern third of the largely Roman Catholic nation under martial law to deal with a siege by pro-Islamic State group militants in southern Marawi city that has dragged on for nearly four months.

Marcos' martial law era, which ended in 1981, was marked by massive human rights violations and muzzling of civil liberties.

"This is the worst administration I have seen," Marina Maulawin, a 74-year-old retired teacher, said of Duterte's presidency. "He's like a madman," she said at the main opposition rally.

A Catholic nun, Sister Mary John Mananzan, expressed relief that more people were starting to stand up against government abuses. "I am happy that we are all here because I can see that just as fear is infectious, courage is also infectious," she said on stage at the opposition rally.

The left-wing group Karapatan accused Duterte of using "narratives and tactics straight out of Marcos's playbook of repression, repeating and justifying rights violations, with increasing frequency and intensity."

Freddie Olase, a 53-year-old driver, joined a few thousand Duterte supporters in a rally in a square beside the popular Quiapo Catholic church.

"What we need is an iron fist," Olase said, expressing support for Duterte's anti-drug campaign. "I now feel safer when going home in our community and my grandchildren can play outside the house even at night."

Duterte warned protesters not to break the law. "I will not hesitate to use force even if it would mean my downfall as president of this country, remember that," Duterte said Friday on state TV.

Waving red flags and carrying placards that read "Stop the Killings," left-wing groups gathered in three areas of Manila, including a bridge leading to the presidential palace. They assembled later at a park by Manila Bay for the main protest.

Another group of protesters staged a separate rally at the Commission on Human Rights, which has been repeatedly denounced by Duterte for raising an alarm over his campaign against illegal drugs that has left thousands of suspects dead.

Duterte's allies in the House of Representatives initially voted to reduce the commission's annual budget to 1,000 pesos ($20) but reconsidered the decision late Wednesday amid an outcry and after the human rights chief met congressional leaders.

U.S. and European Union officials, along with the United Nations and human rights groups, have expressed alarm over Duterte's anti-drug campaign, sparking expletives-laden outbursts from the president. The unorthodox president, however, has remained popular in his crime-weary country, helped by his common-guy demeanor and populist rhetoric.

Duterte said Wednesday he has ordered law enforcers to kill his own children, two of whom serve as mayor and vice mayor of his southern home city, if they're found to be involved in illegal drugs.

"You can just kill them so the people can't say anything," Duterte said.

The Pew Research Center survey released Thursday showed Duterte and his campaign against illegal drugs are supported by most Filipinos, with 86 percent having a favorable view of Duterte and 78 percent supporting his handling of the drug problem.

"Despite international concerns leveled by various governments regarding Duterte's controversial clashes with drug cartels and potential human rights violations, the Filipino leader and his policies are widely popular," Pew said.

It said face-to-face interviews of 1,000 adult Filipinos were conducted between Feb. 26 and May 8 in the nationwide survey, which had a margin of error of 4.3 percentage points.