President of the Philippines Rodrigo Duterte says he has promised God he won’t use expletives again.

Mr Duterte’s profanities have become his trademark, especially when threatening to kill drug dealers as part of his war on illegal drugs that has left thousands dead since he took office at the end of June.

During a flight home from Japan last night, Mr Duterte said the voice of God threatened to crash his plane if he did not change his ways.

"I heard a voice that said ‘if you don’t stop epithets, I will bring this plane down now'", he said. "And I said, ‘Who is this?’ So, of course, ‘it’s God,’. So, I promise God to … not express slang, cuss words and everything"

"So you guys hear me right always because (a) promise to God is a promise to the Filipino people," he promised, as he was met with applause.

"All of you there in the human rights commission are ugly"

He shocked the dominant Roman Catholics last year when he fired an expletive while expressing his disgust over a monstrous traffic jam that trapped him while Pope Francis was visiting Manila.

“I wanted to call. ‘Pope, you son of a bitch, go home.’ Don’t visit here anymore,” he told a mob of supporters, some of whom laughed.

He later apologised after Filipino bishops expressed shock and outrage.

He also previously told President Barack Obama to "go to hell", and said everyone in the Human Rights Commission was "ugly" when asked for a message for a Filipino beauty queen who won the recent Miss International pageant.