China might have acted on its own intelligence when it raised the alert for possible threats to its ships in the Strait of Malacca, but the move may not be welcomed by regional littoral states, maritime experts said.
On Tuesday, China's Transport Ministry, warning of "probable or imminent" threats, raised the security level for Chinese ships to 3 - the highest level.
While littoral states such as Singapore, Malaysia and Indonesia are aware of China's move, they do not appear to share its assessment.
Singapore's Maritime and Port Authority (MPA), responding to media queries, said yesterday it has not received any information on immediate threats to ships sailing through the Strait of Malacca and Strait of Singapore, or to Singapore-registered ships.
It said that Singapore will maintain the current security level of 1 as per the International Ship and Port Facility Security Code.
The International Maritime Organisation said that Level 3 should be an "exceptional measure applying only when there is credible information that a security incident is probable or imminent".
Maritime specialist Collin Koh, a research fellow at the S. Rajaratnam School of International Studies (RSIS), said China might have its own intelligence assessment of the threat that may not have been shared with MPA. He cited an online report by Lloyd's List that said an internal e-mail alert from China's Cosco Shipping Energy Transportation suggested the threat was from Indonesian parties.
Most of China's oil imports pass through the South China Sea via the Strait of Malacca.
"China has long been sensitive about security and safety for its shipping plying through a natural strategic choke point such as the Strait of Malacca, be it a threat posed by a state or non-state actor," Dr Koh said. "So this alert level could have been understandable even though this unilateral move, it seems, may run afoul with the littoral states in the strait who don't desire an alarmist approach," he added.
A Bloomberg report cited Indonesian Maritime Security Agency chief Achmad Taufiqoerrochman as saying the agency was looking into the issue. Malaysia's Transport Ministry declined to comment.
Mr Ben Ho, a naval analyst at RSIS, said China's move was a surprise, given that the maritime security environment has been stable in recent years. He said the threat is unlikely to be from a state source.