Philippine police commandos clashed on Wednesday with armed bodyguards of a town mayor linked to illegal drugs, killing six, officials said, in the latest violence that has left more than 400 suspected drug criminals dead since President Rodrigo Duterte took office. Regional police chief Elmer Beltejar said police were patrolling near the house of Mayor Rolando Espinosa Sr. in the central town of Albuera when they were fired upon by the mayor's bodyguards. The police fired back, killing six bodyguards. The clash came a day after Espinosa surrendered to national police chief Ronald dela Rosa. Authorities allege he has been protecting drug dealers, including his son Erwin, who has not surrendered. Espinosa surrendered inside a 24-hour deadline given to him by Duterte to yield or a "shoot-on-sight order" would be issued against him and his son. Dela Rosa has warned that the younger Espinosa "will die" if he elects to shoot it out with the police. National police spokesman Dionardo Carlos said authorities are looking into reports the younger Espinosa has fled the country. Duterte took office June 30, and since then 402 suspected drug traffickers have been killed in clashes with police, national police records show. At least 4,418 others have been arrested. Duterte, a former prosecutor and mayor of southern Davao city, where he built a reputation for tough anti-crime methods, won the presidential election earlier this year on a promise to end criminality and corruption in the first three to six months of his presidency. He encouraged police and even ordinary citizens to shoot suspected drug dealers if they resist arrest, and promised cash rewards if they turn in drug lords. The moves have sparked alarm among human rights groups, with the New York-based Human Rights Watch saying Tuesday it had signed a joint letter with more than 300 organizations urging the International Narcotics Control Board and United Nations Office on Drugs and Crime to urgently condemn and call for a halt to the killings. "International drug control agencies need to make clear to Philippines' President Roderigo Duterte that the surge in killings of suspected drug dealers and users is not acceptable ‘crime control,' but instead a government failure to protect people's most fundamental human rights," said Phelim Kine , Human Rights Watch's deputy Asia director. Philippine Sen. Leila M. De Lima, in a speech Tuesday decried what she called the "do-it- yourself justice" system under the Duterte. "We must call for the accountability of state actors responsible for this terrifying trend in law enforcement, and the investigation of killings perpetrated by the vigilante assassins," she said.