Philippine President Rodrigo Duterte's eldest son has quit as vice mayor of the southern city of Davao, citing his being linked to a drug smuggling case by opponents and personal problems from a failed marriage as reasons for the move.

Key points: Paolo Duterte says personal problems and being linked to drug smuggling are his reasons for quitting

Paolo Duterte says personal problems and being linked to drug smuggling are his reasons for quitting He was accused of having helped ease entry of a seized shipment of narcotics

He was accused of having helped ease entry of a seized shipment of narcotics Paolo's younger sister Sara Duterte-Carpio remains the mayor of Davao

Paolo Duterte announced his resignation during a special session of the Davao City Council.

Davao is President Duterte's hometown and its mayor is Paolo's younger sister, Sara Duterte-Carpio.

"There are recent unfortunate events in my life that are closely tied to my failed first marriage," the former vice mayor said in a statement made available to media.

"These, among others, include the maligning of my reputation in the recent name dropping incident in the Bureau of Customs, a EUR smuggling case and the very public squabble with my daughter."

Paolo testified at a senate investigation in September into a seized shipment of around $161.7 million worth of narcotics from China.

He testified after opponents of the president, who has instigated a fierce crackdown on the drugs trade, said they believe his son may have helped ease the entry of the shipment at the port in Manila, the Philippines capital.

Paolo has denied any involvement.

More recently, he has been involved in an online spat with Isabelle, his 15-year-old daughter from his first wife.

Paolo has called her "embarrassing" on Facebook after she complained on Twitter about being treated badly by her father.

The president's office, the mayor's office and other members of Paolo's family did not immediately respond to requests for comment.

Reuters