MANILA, Oct 2 (Reuters) - Philippines President Rodrigo Duterte said on Saturday he was retiring from politics, a surprise move that fuelled speculation he was clearing the way for a presidential run by his daughter. Sara Duterte-Carpio is currently mayor of Davao, the Philippines" third-largest city, and filed on Saturday to contest the role again. She has previously said she would not run for national office next year. "Today, I announce my retirement from politics," Duterte said as he accompanied his ally Senator Christopher "Bong" Go of the ruling PDP-Laban party to register Go"s candidacy for vice president in next year"s election. But political analysts were sceptical, noting that last-minute changes were still possible, as in 2015 when Duterte entered the presidential election race at the eleventh hour and won by a huge margin. Duterte, 76, had been expected to run for the No. 2 job, a plan most Filipinos oppose as violating the spirit of the constitution, which sets a one-term limit for the president to stop power being abused. "In obedience to the will of the people, who after all placed me in the presidency many years ago, I now say to my countrymen, I will follow your wish," Duterte said as he urged the public to back his longtime aide. Analysts say it is crucial for Duterte to have a loyal successor to insulate him from potential legal action - at home or by the International Criminal Court - over the thousands of state killings in his war on drugs since 2016. "I would take his announcement with a lot of salt," Carlos Conde, Philippines researcher for New York-based Human Rights Watch, told Reuters. "But assuming that he"s really going to retire, that doesn"t mean he won"t get the protection from the ICC that he craves." Duterte, a maverick leader famous for his embrace of China and disdain for the United States, traditionally a close ally of the Philippines, remains popular even though his opponents accuse him of being authoritarian and intolerant of dissent. Activist and human rights lawyer Neri Colmenares also viewed Duterte"s announcement sceptically, saying "he will still dictate (to) his political machinery". "Unfortunately for him, he will not be spared from accountability. Retirement from politics will not save him from a prison sentence," said Colmenares, who is also providing legal assistance to drug war victims. Philippines President Rodrigo Duterte attends the ASEAN Plus Three (APT) Summit in Singapore, November 15, 2018. REUTERS/Athit Perawongmetha/File Photo Philippines President Rodrigo Duterte attends the ASEAN Plus Three (APT) Summit in Singapore, November 15, 2018. REUTERS/Athit Perawongmetha/File Photo Authorities have killed more than 6,100 suspected drug dealers and users since Duterte took office in June 2016. Rights groups say the police summarily executed suspects, which the police deny, saying they acted in self-defence during sting operations. "ANYTHING CAN HAPPEN" More than 60 million Filipinos will vote in May for a new president, vice president and more than 18,000 lawmakers and local government officials. Political observers had long suspected Duterte could spring a surprise, such as a presidential bid by his daughter next year. Duterte-Carpio"s re-election filing, shortly after her father announced his retirement, did little to douse speculation she has her eye on the presidency. Mar Masanguid, who backed Duterte"s 2016 run and has now founded a group to back Duterte-Carpio, said the signs still pointed to a run, which would mirror her father"s last minute bid in 2016. "In politics, anything can happen," he said. Duterte-Carpio has topped opinion surveys on prospective candidates, but said last month she was not a candidate for higher office next year because she and her father had agreed only one of them would run for a national role in 2022. The older Duterte"s decision not to join the race next year would clear her way. "This allows Sara Duterte to run," said Antonio La Vina, professor of law and politics at the Ateneo de Manila University. "She sees through the father"s scheme or it is a drama to confuse everyone." But La Vina said he could not rule out the possibility the firebrand leader might have a change of heart and be Go"s substitute. Candidates have until Friday to register, but withdrawals and substitutions are allowed until Nov. 15.