MANILA (Reuters) - Philippine President Rodrigo Duterte’s honeymoon period may be over, but his deadly anti-drugs campaign will not wane, his office said on Monday, after a fall in ratings that his opponents said showed public disillusionment with his rule.

Duterte has enjoyed strong opinion poll numbers since winning the presidency in last year’s elections but heavy scrutiny of his war on drugs, which has killed thousands of Filipinos, appears to have impacted his ratings.

Trust and satisfaction in Duterte fell to the lowest of his presidency in the third quarter of this year, a survey showed on Sunday, although sentiment about his leadership remained positive overall.

“The honeymoon period of the president is usually for a year, so this is expected,” Duterte’s communications secretary, Martin Andanar, said in a radio interview, adding it should motivate the government to deliver on its overall objectives.

The Social Weather Stations survey was conducted between September 23-27, two days after thousands of Filipinos rallied to denounce Duterte’s drugs war and his authoritarian leadership style.

The high death toll has stoked international alarm, although domestic polls have shown Filipinos are largely supportive of his tough measures to fight crime and drugs.

Police say they have killed 3,900 drug suspects during their anti-narcotics operations and deny executions have taken place, as human rights groups have alleged.

Philippines 'President Rodrigo Duterte stands at attention during a courtesy call with the Association of Southeast Asian Nations (ASEAN) Economic Ministers in Manila, Philippines, September 6, 2017. REUTERS/Pool/Mark Cristino

But the campaign has been under the microscope of late, due largely to the high-profile killing by police of a 17-year-old student on Aug. 16, which led to a senate probe. A murder investigation is under way.

Police said he was a drug suspect killed because he opened fire on them while resisting arrest, but security camera footage showed him in police custody. His family insists he was executed.

Staunch critics of Duterte were quick to take advantage of a survey slump they said reflected public discontent and scepticism about his drugs war.

“It’s very encouraging to know that the Filipino people are beginning to see the light,” said Senator Antonio Trillanes, a fierce opponent who has recently accused Duterte of concealing assets when he was Davao City mayor.

“They are now seeing Duterte for who he really is: a lying, rude, amoral, corrupt and oppressive former mayor who is totally incompetent about governance at the national level.”

Presidential spokesman Ernesto Abella also said the honeymoon was over, but Duterte was not motivated by popularity ratings and was “bent on making sure that he addresses the three campaign themes which is crime, corruption and illegal drugs”.

Duterte’s office frequently cites polls, including SWS, as a sign of his public support.

Peace and order are also one of the cornerstones of the 72-year-old leader’s economic agenda, which aims to lift the country’s growth to 7-8 percent during his six-year term.

Senator Risa Hontiveros said the ratings dip showed Duterte’s “authoritarian style of governance is losing its appeal and support”.

“The writing on the wall is simple and clear: President Duterte cannot govern based on fear, lies and killings,” Hontiveros said in a statement.