Although Duterte did not mention Locsin by name, presidential spokesman Harry Roque later confirmed that the president was referring to the foreign secretary.

Roque added: “We reiterate the president’s message that curse words have no place in diplomacy” and “President Duterte told members of his cabinet that he is the only one who can use curse words. His cabinet members should not copy him.”

Roque said Locsin had apologised on his own accord and had not been not ordered to do so.

He said Locsin had personally apologised through the Chinese ambassador Huang Xilian.

In a series of tweets on Tuesday morning Locsin also apologised to Wang Yi, saying he was sorry for hurting his feelings and that the Chinese foreign minister was his “idol in diplomacy”.

“I just don’t want to lose my friendship with the most elegant mind in diplomacy with manners to match,” Locsin said.

He blamed his foul words on his “hair-trigger temper”, which he said was a family trait.

South China Sea heats up as Philippines drops the F-bomb over Chinese boats

NOT AMUSED

The Chinese foreign ministry was unamused by Locsin’s attempt to smooth things over.

Hours after the apology, ministry spokesman Wang Wenbin said: “We hope that a certain individual from the Philippine side will mind basic manners and act in ways that suit his status”. He reminded Locsin that “megaphone diplomacy can only undermine mutual trust, [not] change reality”.

Wang said that Huangyan Island, as China refers to Scarborough Shoal, was Chinese territory and that the adjacent waters were under China’s jurisdiction.

“China urges the Philippine side to earnestly respect China’s sovereignty and jurisdiction, and stop taking actions that may complicate the situation,” Wang said.

Locsin then replied with a Tweet that suggested to some observers he might not be entirely repentant.

“Damned decent of them not to mention my name. I will mind basic manners and act as I’ve usually done in ways that suit my status. I did it well with China in the UN. I just lost it. But these constant provocations … no they’re no excuse for dropping manners.”

Analysts said Locsin’s outburst had undermined his effectiveness as a diplomat and his apology was a form of damage control.

A senior government official, who spoke on condition of anonymity, said while the apology had cleared up “any possible misunderstanding due to the use of undiplomatic language”, neither side had changed its position on the deeper issue of the territorial dispute.

Asked whether Locsin should resign, retired diplomat Larry Baja disagreed, saying Locsin merely apologised “for his language, not on the substance” of what he said.

However, Baja suggested Duterte may have undermined the Philippines’ position during his television appearance in which he cautioned against being “rude and disrespectful”.

At another part of the show, referring to the differences over Scarborough Shoal, Duterte had asked China to “kindly just allow our fishermen to fish in peace”.

Baja said the use of the word “allow” implies “you are asking permission from China. It implies a diminution of the Philippines’ right to its exclusive economic zone”.

Meanwhile, some people in the Philippines suggested Locsin had no real need to apologise.

Calling Locsin a “knight of the King’s English”, Senator Ralph Recto came to his defence, saying “in an era when diplomacy is practised by those who ‘speak softly and carry a selfie stick’, it pays to have a foreign affairs secretary who is brave and brilliant because it will allow our country to punch above its weight”.

“While we may not have missiles to launch, we possess something more potent – Locsin missives, against which no shield has been proven effective.”