The vice mayor of a southern Philippine city has offered a $121,000 reward for the decapitated head of the alleged leader of a gang of car thieves.

Davao City Vice Mayor Rodrigo Duterte, known for being tough on criminals, told a news conference in Davao on Wednesday that he would give 2 million pesos ($48,400) if suspect Ryan Yu is arrested and 4 million pesos ($96,800) if he's killed. He said he'd add another 1 million pesos ($24,200) if Yu's decapitated head is delivered to him "on ice."

Davao police chief Ronald de la Rosa said Friday that he had received text messages from people seeking assurances the reward offer was real. He said they should cooperate with police.

Human rights commission chairman Loretta Rosales said Friday that Duterte violated the law by passing a sentence on Yu without due process.

Duterte's offer comes as he runs virtually unopposed to regain his seat as mayor of Davao. His daughter is currently the mayor but won't seek reelection. His son, Paolo, is running as his vice mayor.

Rosales urged Interior Secretary Mar Roxas to take action against Duterte, who has been indirectly linked to a "death squad" that was responsible for over 200 killings of suspected criminals, including some minors, when he was mayor from 2004 to 2009. He has denied any involvement.

"What he says ... is irresponsible coming from a person of authority," Rosales said. "That is an extrajudicial killing. He is justifying extrajudicial killing."

Duterte told reporters that Yu had made unfounded allegations of car smuggling against his son, Paolo, late last year and that received a call from Roxas on behalf of President Benigno Aquino III asking about the allegations.

It is not known where Yu is, or if he is still in the Philippines.

Duterte said the offer was prompted by the recent discovery of a compound where cars allegedly stolen by Yu's gang were being stored, adding the offer was open to anyone or any group, including Muslim and communist rebels.

"Make your choice. Either you want to earn 2 million, or you want to earn 4 million, or if you want to be morbid about it — bring the head of Ryan Yu to me and I will add 1 million," he said. He suggested putting the head in an ice bag "so it won't smell bad."

He said the money will come from contributions to his election campaign.

De la Rosa said offering a reward for an arrest is legal, adding that if Yu resists his death could be justified. "I have no comment about that," he said when asked about the reward for the decapitation.

He urged the public to cooperate with police officers, who will share in the reward. "Otherwise we will have so many Ryan Yus or people who look like him dead," he said.