Philippine senator battles President Rodrigo Duterte

But the former Navy officer with a history of coup attempts appears to thrive on the pressures that have come with regularly accusing President Rodrigo Duterte of being a corrupt mass murderer.

"This man is a sociopath and he has the mindset of a hitman," Trillanes, 46, told AFP in an interview on Wednesday from his senate office, offering a typically incendiary assessment of his rival.

Duterte won last year's presidential elections on a brutal law-and-order platform in which he promised an unprecedented campaign to eradicate illegal drugs in society by killing up to 100,000 traffickers and addicts.

He vowed so many bodies would be dumped in Manila Bay that the fish would grow fat from feeding on them, and said he would pardon police if they were found guilty of rights abuses while enacting his drug war.

Since Duterte assumed office in the middle of last year, police have reported killing more than 3,800 people while thousands of others have been murdered in unexplained circumstances.

Many Filipinos looking for quick solutions to crime continue to support Duterte, according to polls, and he enjoys majority backing in both houses of Congress.

Dictatorship fears

However a climate of fear has also emerged, with critics warning the president is determined to silence dissenters and drag the Philippines back into a dictatorship three decades after a "People Power" revolution ousted Ferdinand Marcos.

Duterte has launched tirades against the Supreme Court chief justice, the Commission on Human Rights, the Catholic Church and critical media outlets. He and his allies have then started campaigns to curb their powers or discredit them.

Senator Leila de Lima, who had been one of the most vocal critics alongside Trillanes, was in February jailed on drug trafficking charges she says were fabricated. Rights groups describe her as a political prisoner.

On the weekend Duterte made Trillanes his new top target.

"I will destroy him or he will destroy me," Duterte told reporters.

This came after Trillanes had Duterte's son, Paolo, brought before a Senate inquiry last week to face allegations he was involved in drug trafficking.

Trillanes accused the younger Duterte of being a member of a Chinese triad that imported huge amounts of methamphetamines into the Philippines, and challenged him to show a tattoo on his back that allegedly proved he was a member of the gang.

Paolo Duterte acknowledged he did have a tattoo on his back, but refused to show it and rejected all accusations against him.

Since Duterte's "destroy" remark, his officials and social media supporters have accused Trillanes of hiding ill-gotten wealth in secret bank accounts.

Trillanes denied those accusations, telling AFP they were an expected part of Duterte's counter-offensive, and that worse could come.

"Duterte actually ordered a hit on me. He wants me killed. Aside from the fact he wants cases fabricated so I can be put away (in jail) like Senator De Lima," the father-of-two teenagers said.

Even though he has called for so many killings, Duterte has repeatedly insisted that he would not act outside the law nor allow state-sponsored murders.

Crazy brave

Trillanes showed no signs in the interview of being intimidated by Duterte, likely drawing on his many years of experience in the Philippines' bare-knuckled democratic ring.

As a young naval officer, Trillanes helped lead two brief coup attempts against then-president Gloria Arroyo in 2003 and 2007.

Trillanes and his military allies accused Arroyo of corruption, state-sponsored terrorism and subverting democracy on multiple fronts.

He was jailed for seven years but, in what was widely seen as an anti-Arroyo vote, became the first person to be elected a senator while in jail.

Duterte's predecessor, an Arroyo critic, pardoned Trillanes and other coup plotters in 2010.

This allowed Trillanes to pursue his senate career at full throttle -- and he became well-known for digging up dirt on a range of powerful politicians.

To his supporters, Trillanes became a crazy brave anti-graft crusader.

His critics saw him as a publicity hound chiefly concerned with advancing his political career.

Trillanes rejected those accusations, insisting he would walk away from politics when his Senate term ended in 2019 to initially pursue a masters degree in international relations.

"In this political fight with Duterte, there is no forthcoming election for me," Trillanes said as he defended his motives.

"And most importantly my life is at stake here. So I believe no political ambition could ever match up to that."