Philippines President Rodrigo Duterte has promised to stop using abusive words in his speeches after a perceived "warning from God", local media reporters on Friday.

"I was looking at the skies...A voice said that you know 'If you don't stop, I will bring this plane down now'," Duterte told reporters after returning from a three-day official visit to Japan.

"And I said, who is this? Of course, it's God. Oh, OK. So, I promised God not to use slang, cuss words," he said.

"A promise to God is a promise to the Filipino people," Duterte added according to reports.

Duterte, who took office on June 30 after his overwhelming victory in the presidential elections, is known for constantly swearing during his speeches and press conferences, Efe news reported.

He is especially partial to "putang ina", which translates as "son of a bitch" and which he used against US President Barack Obama, US Ambassador in Manila Philip Goldberg and Pope Francis.

Moreover, Duterte has also often asked the US to "go to hell" among other things, for criticising his violent anti-drug campaign in the Philippines, which killed more than 4,700 in four months.

He also bad-mouthed the European Union, as well as the UN just before a meeting with its Secretary General Ban Ki-Moon in September in Laos.

Despite criticism from the international community for his attitude, Duterte is hugely popular in the Philippines.

According to latest surveys, 76 per cent of Filipinos approves of the president's controversial management of affairs, while only 11 per cent expressed dissatisfaction and 13 per cent were indecisive.