LOS BAÑOS, Laguna - Davao City Mayor Rodrigo Duterte on Friday said the camp of President Benigno Aquino III should think twice before filing cases against him over his alleged involvement in extrajudicial killings.

Duterte's campaign spokesperson has said they have information that charges are now being prepared against the PDP-Laban standard-bearer.

Duterte questioned the timing of the possible filing of charges against him. Asked if his good survey ratings could be the motivation behind the supposed cases, he merely said: "Bring it on."

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The mayor, however, insisted that he was never involved in any extrajudicial killing.

He had admitted participating in the execution of criminals in his city, but said that killing criminals who commit heinous crimes is not a crime.

He also said that he is not in favor of extrajudicial killings "in the sense na [papatayin] yung nakatali yung kamay sa likod tapos nakaluhod."

Duterte lambasted former Justice Secretary Leila de Lima, who is now running for senator under the Liberal Party (LP), saying they have no evidence to pin him down on the alleged extrajudicial killings.

He noted that De Lima has threatened filing cases against him based on several media interviews and speaking engagements, but she has not done so until now.

Asked if he is bothered by the possible filing of cases, Duterte just said: "It takes two to tango."

"Kahit nasa bottom ka, target ka pa rin ng ganyan. Si De Lima, matagal na niyang sinasabi yan, so be my guest," he added.

The Duterte-Cayetano tandem was in Los Baños to discuss their platform of government to farmers.

Malacañang, for its part, denied any move to destroy Duterte's chances in the May 9 presidential race.

"Walang proyekto ang gobyerno na siraan si Mayor Duterte o sino mang kandidato," said Communications Secretary Sonny Coloma. - With a report from Willard Cheng, ABS-CBN News