SINGAPORE, Jan 9 ― Singapore Defence Minister Ng En Hen called on Hong Kong to return nine armoured personnel carriers seized by customs officials late last year, saying the equipment was sovereign property and could not legally be held.

Ng told parliament that Singapore had shipped troop carriers commercially for 30 years without incident, and that Singapore and Hong Kong had long enjoyed good and friendly relations.

"The Hong Kong authorities have responded that the investigation is ongoing and will take some time to complete,” Ng said. "Adherence to the rule of law has been the fundamental basis for peace and stability in the last half century in Asia.”

Singapore has been left seeking answers for almost six weeks, with no word from Hong Kong customs as to why the SAF Terrex Infantry Carrier Vehicles were seized en route from Taiwan on a commercial ship after being used in training exercises.

Hong Kong’s Customs and Excise Department said the case was under investigation. "The suspected controlled items are still kept at a storage place of customs in Tuen Mun,” it said today in an e-mailed statement. "They have been stored indoors since December 6.”

The shipment prompted a formal protest from Beijing, which warned Singapore to follow Hong Kong law and the One-China principle that China uses to guide its affairs with Taiwan, which it considers a province. Foreign Affairs Minister Vivian Balakrishnan told parliament that Singapore’s relations with China should not be seen as a zero sum game. "We must also maintain our emphasis on upholding international law and scrupulously respecting agreements entered into with other countries,” he said.

The seizure raised tensions between the two nations, with China in recent months bristling at Singapore’s perceived alignment with the US against Beijing’s actions in the disputed South China Sea.

While any spat with its largest trading partner threatens to distract Singapore from its preferred focus on trade and investment, failure to get the vehicles released could also risk a backlash at home, especially after the US secured the return of a drone seized by China in the South China Sea within a matter of days.

‘Relevant laws’

China’s foreign ministry said in a regular briefing last week that Hong Kong was "handling the issue in accordance with relevant laws and regulations.”

The dispute highlights some of the potential pitfalls for smaller Asian nations as they seek to stay neutral amid a regional battle for influence between China and the US Singapore’s Prime Minister Lee Hsien Loong has spoken previously of the importance for countries in Southeast Asia not to have to pick a side.

Singapore, a tiny island-nation that regularly trains its troops overseas, has strong historical and cultural ties to China. Many residents are descendants of traders from the mainland, and in late 2015 Singapore hosted the first summit between the presidents of China and Taiwan since their civil war. At the same time, it has strengthened military ties with the US, allowing Poseidon surveillance aircraft and littoral combat ships to operate out of its territory. ― Bloomberg