Filipino president vows to stop swearing

AAP

Philippine President Rodrigo Duterte has promised to stop swearing, saying God spoke to him on a flight from Japan on Thursday, warning him the plane would crash if he kept using bad language.

The maverick former mayor, famous for profanity that has included outbursts aimed at Pope Francis and US President Barack Obama, said he heard a voice and realised it was God, telling him to clean up his act.

"I was looking at the skies while I was coming over here ... everybody was asleep, snoring, but a voice said that, 'you know, if you don't stop epithets, I will bring this plane down now'," Duterte said at a news conference late on Thursday upon arrival in his home city of Davao.

"And I said, 'who is this?' So, of course, it's God. OK.

"So, I promise God ... not to express slang, cuss words and everything."

Duterte, a former outspoken city mayor, emerged as a brash, crass, alternative candidate in a May election which he won by a big margin, owing much to his earthy style and promises to tackle problems important to ordinary people, like drugs and crime.

Alan Peter Cayetano, Duterte's vice-presidential running mate and now his foreign affairs adviser, said Duterte was tired and appeared pensive during the flight back from Japan.

"He felt it was a message from God," Cayetano told reporters on Friday.

"I've always felt he's a deeply spiritual person. He's not religious, but he believes in God."