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MANILA -- A man who claimed he was the hooded man "Bikoy" in a series of web videos that linked President Rodrigo Duterte's family to illegal drugs said he tried but failed to establish that the chief executive's long-time aide had a tattoo on his back.

The alleged dragon tattoo, according to the videos, would link Christopher "Bong" Go to an international drug syndicate. Go, who won a Senate seat in the May 13 vote, denied this and showed his bare back to news cameras.

"Hindi totoo. Walang dragon tattoo si Bong Go," said Peter Advincula, who is in police custody.

(That's not true. Bong Go has no dragon tattoo.)

"Naghanap talaga kami ng paraan para palitawin na may tattoo siya," he said.

(We tried to find a way to make it appear that he has a tattoo.)

Advincula cited an edited photo of Go, taken during a basketball tournament, where a part of his back was showing.

He said he had not personally seen the back of the President's son, Davao City congressman-elect Paolo Duterte, who according to the video also had a dragon tattoo.

Advincula claimed the camp of outgoing Sen. Antonio Trillanes offered him P500,000 to take part in the video. Trillanes, the President's most vocal critic, has yet to issue a statement.

Senate President Vicente "Tito" Sotto had cast doubt on the credibility of Advincula, saying the man who claimed to be "Bikoy" also tried to link officials of the Aquino administration to the illegal drug trade in 2016.