The spokesman for Philippine presidential front runner Rodrigo Duterte has said that Mr Duterte's remarks about burning a Singapore flag were made "jokingly".

In a Facebook post yesterday morning, spokesman Peter Tiu Lavina said Mr Duterte's remarks were a "tit-for-tat" for Singapore's reaction to a Facebook image that had been circulating implying that Singapore's Prime Minister had endorsed Mr Duterte's candidacy.

"How can a self-respecting country react to such trivial matter and calling for investigation?" said Mr Lavina.

"Now, it has tasted its own dose of medicine when Duterte retorted jokingly that he will burn the Singaporean flag again. It's a tit-for-tat. Only the onion-skinned would actually be affected."

On April 22, the Singapore Embassy in Manila said on its Facebook page that a Facebook post "mischievously alleging" that Mr Lee Hsien Loong had endorsed a presidential candidate was untrue.

The embassy said that Singapore does not endorse any candidate and added: "The choice is for Filipinos alone to make. We wish the Philippines well in the conduct of its elections."

The embassy did not name Mr Duterte, but a post that was circulating showed a photo of Mr Lee with a quote attributed to Mr Lee saying: "Mayor Rodrigo Duterte is the only presidential candidate that could make Philippines like Singapore. Clean, efficient and disciplined."

On April 25, the embassy posted again on Facebook saying it "takes a serious view of the misleading FB post. We are seeking legal advice. We also request the immediate removal of the post, which is a clear misrepresentation."

On April 30, Mr Duterte, the mayor of Davao City, spoke at a rally in Daet town in Camarines Norte province, 330km south of the capital Manila.

On stage, he recalled how in 1995 he had protested against Singapore's execution of Filipino maid Flor Contemplacion, who had killed a fellow Filipino maid and a four-year-old Singaporean boy.

Mr Duterte told the crowd that he recalled being informed that a "Singapore spokesman" had told then President Fidel Ramos, who was appealing Contemplacion's conviction: "No, even if you're President of the Philippines, I will not entertain any..."

He told his supporters that he had told someone at the time: "Find me a flag of Singapore. Let's burn it. I told them, **** Singapore."

He led about 1,000 Davao City employees in burning the Singapore flag in March 1995.

In Mr Lavina's Facebook post yesterday, he said: "Duterte practices the golden rule - if you treat me well, I will treat you well as well. If you bash me, I return the favor. This is also the context about Singapore's complaint that its Prime Minister was used in 'endorsing' Duterte.

"It was a meme. A humorous image in social media which is an open space, meaning anyone could have made that up. How can a self-respecting country react to such trivial matter and calling for investigation?

"Now, it has tasted its own dose of medicine when Duterte retorted jokingly that he will burn the Singaporean flag again. It's a tit-for-tat. Only the onion-skinned would actually be affected."

Mr Duterte, 71, is no stranger to making controversial statements.

In November last year, he "cursed" Pope Francis for causing traffic jams in Manila during his January visit to the Philippines.

Last month, a YouTube video showed Mr Duterte joking that he should have had the first turn at an Australian missionary brutally raped and killed during a prison riot 27 years ago.

After the Australian and American ambassadors criticised him for the rape joke, Mr Duterte said he was prepared to sever ties with the two countries if he wins the May 9 election .

Mr Duterte has been leading in surveys on who Filipinos want to be their next president. His nearest rival is Senator Grace Poe.