MANILA - Presidential race frontrunner Rodrigo Duterte sought the support of the country's business elite on Wednesday with a profanity-laced vow to kill criminals and grow the economy.

"Relax, I am not the man I am portrayed to be by some," Duterte said to nervous laughter from members and guests of the Makati Business Club.

The 71-year-old mayor of Davao City said he would hire an additional 3,000 policemen and would double the salary of security forces to start a bloody war against crime, the effects of which, would be felt within weeks.

"I am castigated for being brutal and honest. It will be a bloody war, and for those who are already there, they will never go back," he said.

"You need a mayor to say: I am in charge," he said, as he took a swipe at his rivals.

Duterte said he would implement infrastructure projects that were held up under past governments due to a lack of "political will."

"We have to continue with public spending and we have to continue the projects that will ease up congestion in traffic," he said.

He said he would also continue the conditional cash transfer program, which gives the poorest o the poor a monthly allowance as long as they keep their children in school.

"I will not hesitate to copy the projects of Noynoy (Aquino) or (Gloria) Arroyo that will redound to the benefit of the people. Hindi ako nahihiya mangopya."

The prospect of a Duterte presidency appeared to unnerve investors as the Philippines posted a net outflow of foreign funds in April, bucking a trend of net inflows for emerging markets, BDO Unibank chief investment officer Fedrico Rafael Ocampo told ANC on Tuesday.

Foreign fund outflows show poll jitters: BDO

Duterte widened his lead over nearest rival Sen. Grace Poe in the most recent surveys by Pulse Asia and Social Weather Stations (SWS), despite public outrage over his joking about the rape of an Australian missionary in 1989.

Duterte defended the joke during the MBC luncheon on Wednesday.

"It was slang, galit lang, buti pa itong animal na ito pangit naman ang ganda ng asawa, you are derogating his manhood," he said.

It was the latest in a string of controversial antics by the motorcycle-riding mayor. He has cursed at Pope Francis for causing traffic jams during his January 2015 visit to Manila and kissed scantily-clad women in the mouth during campaign rallies.

He also vowed to ride a jet ski to one of China's artificial islands in the disputed South China Sea to plan to plant the Philippine flag there.

Duterte claims he transformed the southern metropolis of Davao into one of the country's safest cities during his family's over two-decade reign.

Human rights groups however accused Duterte of tolerating vigilante "death squads" that have targeted the city's petty criminals, some of them minors.

Top Philippine candidate pushes 'kill criminals' message