Indonesia is investigating two of its citizens for being part of a Singapore Armed Forces (SAF) contingent in a joint military exercise earlier this month in Magelang, Central Java.
The Indonesians are Singapore permanent residents (PRs) who are full-time national servicemen (NSFs). They went to Central Java for the joint exercise.
When the Indonesian military found out their nationality, the pair were asked to remain at their military dormitory. They were not allowed to participate in the exercise, said Major-General Fuad Basya, the Indonesian Armed Forces (TNI) spokesman.
Singapore's Ministry of Defence said in response to queries: "The two NSFs, who are Singapore PRs, were part of the unit participating in an annual bilateral exercise between the SAF and the TNI to enhance military ties.
"However, they were withdrawn from the exercise and brought back to Singapore. They did not participate in the bilateral exercise."
Under Indonesian law, it is an offence for citizens to serve a foreign military, and those who do so risk being stripped of their citizenship. But the law will take into account those Indonesians who study in countries that adopt mandatory national service.
Indonesia has in the past asked Singapore to exempt its citizens who are PRs from performing national service.
But in Singapore, male PRs are liable to be called up for national service.
"Going forward, Singapore will not send Indonesians to a joint exercise here. We have asked them that, and they are agreeable," Maj-Gen Fuad told The Straits Times.
This month's Safkar Indopura, which was held for nine days from Nov 4, was the 26th year the joint exercises were carried out, Antara news agency reported last week.
An Indonesian Foreign Ministry official told The Straits Times that the matter of the two national servicemen was being handled by the Defence Ministry.
This issue of Indonesians serving in the SAF is not new.
In 1999, then President B. J. Habibie ordered, after a Cabinet meeting, that the citizenship of Indonesians living in Singapore who served national service be revoked, as the country does not recognise dual citizenship.
In 2008, then Foreign Minister Hassan Wirajuda asked Singapore to exempt Indonesian citizens who are PRs from performing national service, saying they risked losing their citizenship.
The issue was raised in 2008 following another controversy over the alleged recruitment of Indonesians into the Askar Wataniah, a paramilitary wing of the Malaysian army in Borneo where the two countries share a land border.
In the latest case, Indonesia's Foreign Ministry official Krisna Djaelani was quoted by the Detik. com news website as saying: "There were two Indonesians who are known to have taken part in a joint exercise with the Indonesian military.
"Under Singapore law, permanent residents have the same rights and responsibilities as citizens. So they are obliged to undergo compulsory military training."
But Mr Krisna, who is the ministry's Indonesian workers protection and legal aid director, said that under Indonesian law, Indonesians who serve foreign militaries "will automatically lose their citizenship".
He added: "Now we are working with the Law and Human Rights Ministry. This is under the ministry's jurisdiction."
Yesterday, Mr Krisna was quoted by Detik.com as saying during a media conference that the issue had been dealt with. But he did not elaborate.