Philippine President Rodrigo Duterte could face impeachment after he spoke about looking for "criminals" to kill while he was mayor of Davao City, two senators said on Thursday.

"That is betrayal of public trust and that constitutes high crimes because mass murders certainly fall into the category of high crimes. And high crimes is a ground for impeachment under the constitution," said Senator Leila de Lima, a staunch Duterte critic, told CNN on Thursday.

Senator Richard Gordon, an independent who heads the senate justice committee, also said Duterte's comments opened him up to possible impeachment hearings.

"When he says that, he's opening himself up, so what's the legal way, then go ahead and impeach him," he told reporters, adding he was not surprised by Duterte's comments.

The Philippine president made the comments during a speech on Monday to business executives at the presidential palace, sparking international outcry.

"In Davao, I used to do it personally. Just to show to the guys that, if I can do it why can't you?" he said. 

"I go around in Davao with a motorcycle, with a big bike around and I would just patrol the streets and looking for trouble also. I was really looking for an encounter to be able to kill."

'He always exaggerates'

His government and other allies have dismissed concerns over the comments, saying Duterte's comments were exaggerated to send a warning to criminals.

"The president always resorts to hyperbole, he always exaggerates just to put his message across," Justice Secretary Vitaliano Aguirre II told reporters on Wednesday.

Aguirre added that even if Duterte committed the killings, it did not necessarily mean the president violated the law.

"It could be done with a justifiable cause and justified circumstances as a public officer in order to arrest but if they resisted. He must have been forced," the justice minister said.

Even if Duterte's opponents were to file an impeachment motion in Congress, they would be fighting an uphill battle.

There are less than 50 opposition lawmakers in the Philippines 293-member lower house of Congress, but a two-thirds vote is needed to impeach a president.

Duterte, who took office in June, has been widely criticized internationally for his brutal crackdown on illegal drugs which has led to the deaths of over 2,000 suspects in gunfights with police. Almost all were shot when they resisted arrest.

Another 3,000 other drug-related killings are being investigated by authorities, with critics calling them vigilante killings.

rs/msh  (AFP, Reuters)