Frustrated members of the football fraternity have called on the Football Association of Singapore (FAS) to mete out stern punishments to the six national Under-22 players who broke the team's curfew at the SEA Games in the Philippines.

The FAS named the six players - Zharfan Rohaizad, Joshua Pereira and Lionel Tan (all 22), Kenji Rusydi and Zulqarnaen Suzliman (both 21), and overaged player Tajeli Salamat, 25 - yesterday.

Sources close to the matter told The Straits Times the players were in their rooms when team officials made their rounds at the curfew time of 11pm on Sunday night, after Singapore's 3-0 loss to Thailand.

But they allegedly left later to visit the casino at Solaire Resort and Casino, not far from the team's Manila base at the Century Park Hotel, returning only in the wee hours.

In a statement, the FAS said the actions of the six players were "wholly unacceptable" and revealed that they would face a disciplinary hearing upon the team's return to Singapore, which was scheduled for last night.

"Unless there are compelling justifications, these players can expect to face stiff sanctions from the FAS," added a spokesman in a media statement.

The Singapore National Olympic Council (SNOC) had also said on Thursday that the six "were given a stern formal warning and will face disciplinary hearings upon their return to Singapore after the SEA Games".

Ex-football administrator Patrick Ang, a former general manager of the Singapore team in the Malaysia Cup in the early 1990s, said it was high time the FAS took decisive action to instil discipline in players.

"We have seen disciplinary problems even at senior level and since the days of Raddy Avramovic (former Lions coach from 2003 to 2012)," noted Ang, 69, a former chairman of Singapore Premier League side Geylang International.

"This type of behaviour cannot be accepted when players are representing Singapore. And overseas at an international competition, when you are carrying the flag.

"Stern action has to be taken and I think the authorities will do what is appropriate."

Another long-time administrator, who asked not to be named, also suggested tough action has to be taken so players will be deterred from such behaviour in the future.

"I would go so far as to say ban them from football for a period, so the message really gets through," he said. "Hit them where it hurts - their pockets - with a six-month ban from all football, and a permanent ban from featuring for the national team at any level."

Senior national team skipper Hariss Harun, often held up as a model of professionalism, was dismayed by the news. He represented Singapore at four editions of the SEA Games, winning bronze medals in three.

"It's disappointing to know Singapore football will continue to have negativity associated with its name, especially considering how badly the campaign turned out," said the 29-year-old, who is also captain of Malaysia's Johor Darul Takzim.

"The players have to understand the SEA Games is not just a football tournament; you are part of (a contingent) with so many other athletes from so many other sports."

R. Vengadasalam, the outspoken former long-time general manager of now-defunct local club Woodlands Wellington, said strong action would only impact individual players, but a shift in mindset of discipline by local teams and clubs needs to take place too.

"I am not shocked such a thing has happened," said the 59-year-old. "Local players often keep late nights, and many go to Johor to have supper or just hang out.

"As professionals, they should train, and at night go home, have a good rest and a good sleep. But this is the attitude of young local players in Singapore, and this cushy lifestyle of enjoying the nightlife has to go."

In the FAS' statement, SEA Games head coach Fandi Ahmad said he was "utterly disappointed" with the six offenders.

In his first public comments on the matter, he added: "They are here not only as representatives of the FAS but also Team Singapore and should have known the value of the flag they are bearing.

"This was another unnecessary setback for the team in what turned out as a difficult campaign for us."

On Thursday, the Young Lions ended their Games campaign with an inconsequential 7-0 win over Brunei, having already been eliminated after a 1-0 loss to Vietnam two days earlier.

They finished fourth in the six-team Group B with one win, one draw and three losses. They did not advance to the semi-finals for the third straight Games, after earning a bronze in 2013.