SINGAPORE - More than 40 Singaporeans still remain in conflict-ridden Yemen, according to estimates from the Ministry of Foreign Affairs (MFA).

Despite repeated attempts by the ministry to get them to leave the country for their safety, most of the 40 students, housewives and businessmen have chosen to stay.

Law and Foreign Affairs Minister K Shanmugam on Wednesday urged Singaporeans there to leave immediately and not put themselves at serious risk.

"The more they continue to be there, the more they are putting themselves at risk, and it becomes more and more difficult for any sort of rescue operations to be conducted," said Mr Shanmugam. "The government has a duty to try and help our citizens in situations like this but at the same time, people also have an individual personal responsibility not to put themselves at risk."

A total of 25 Singaporeans have left Yemen over the past two weeks, including a woman who was evacuated on Tuesday.

The MFA has deployed a Crisis Response team in Oman and is planning another wave of evacuations later this week.

The ministry has issued three travel advisories on Yemen since September last year.

Mr Shanmugam drew some lessons from the country's previous experience in helping Singaporeans leave Syria.

"Despite many advisories, some of our people did not leave Syria in time and then they found that all their escape routes were cut off and leaving Syria became extremely difficult."

Similarly, he said that many embassies on the ground in Yemen have closed down and are winding down rescue operations.