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 (Oct 9), after a fall in ratings that his opponents said showed public disillusionment with his rule.

Mr 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 Mr 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.

Mr Duterte's net trust rating, which gauges public sentiment about his personality, was "very good" at 60 points, down from the "excellent" 75 he achieved in the previous poll. The survey was conducted just a few days after thousands of Filipinos rallied to denounce Mr Duterte, his anti-drug crackdown and what they called an emerging dictatorship.

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

The SWS survey did not ask respondents to give a reason for the rating of Mr Duterte, who took office in June 2016. Mr Duterte's spokesman did not immediately respond to a request for comment on the survey results.

Political analyst Ramon Casiple, head of the country's Institute for Political and Electoral Reform, said it was normal for a president's rating to fall during his time in office, but concern over the high death toll in Mr Duterte's signature war on drugs will have weighed on sentiment.

Activists accuse Mr Duterte of inciting police to kill drug dealers and users, which he denies. Police reject allegations they are executing suspects and say deaths occurred because victims had violently resisted arrest.

Mr Casiple said that though the poll still showed Mr Duterte had the support of Filipinos, he should take it seriously.

"This is a real diminution of his popularity and it serves as a wake-up call for him to stop it further going down," Mr Casiple said of the poll. "However, this is still a comfortable figure and far from the threshold of unpopularity."

Thousands of Filipinos have been killed in the crackdown and other SWS polls conducted in September indicated doubts about the validity of official accounts of the 3,800 cases where police killed drug suspects. 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.

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 Mr 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 per cent 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," Ms Hontiveros said in a statement.