Two Chinese warships en route to the site where the missing Malaysia Airlines plane may have crashed will arrive at the surrounding waters within 24 hours, on a major mission to boost the search-and-rescue effort.
China's fastest missile escort, the Mianyang, set off from the waters around the Spratly Islands on Saturday night, and would arrive at the area where the plane was last spotted - a location overlapping the waters of Malaysia and Vietnam - as early as this morning, state-run Xinhua reported yesterday.
Another vessel, the Jinggangshan, one of the largest amphibious ships of the Chinese navy, set out from Zhanjiang city in Guangdong province early yesterday morning, and was expected to arrive at the site tomorrow morning.
The vessel is loaded with life-saving equipment, underwater detection devices and supplies of water and food.
Two helicopters, 30 medical personnel, 10 divers and 52 marines are also on board.
The decision to deploy the two vessels for rescue operations was approved by the Central Military Commission, headed by President Xi Jinping.
The South Sea Fleet has stepped up communications with other parties involved in the rescue operations.
The deployment of the military vessels came after Chinese coastguard vessel 3411 had already entered waters near the site.
Its radar had detected eight vessels, and established communications with two rescue ships from Malaysia, China's State Oceanic Administration said.
On Saturday, Xi ordered relevant authorities to make an "all-out emergency effort".
The rescue operation was complicated not only by the difficult geographical conditions of the area, but also fraught by the tricky geopolitical situation that resulted from the conflicting territorial claims of Malaysia, Vietnam and China over the South China Sea, military and security experts said.
"It is difficult for China to immediately send military vessels for the rescue operation because the incident has not happened in China," said Li Andong, deputy head of the People's Liberation Army General Armaments Department.
Professor Fu Kuen-chen, a Taiwanese expert in maritime law, said the Chinese vessels could play a "supporting role" in a rescue operation that was mainly directed by Vietnam and Malaysia, and that the PLA ships needed to get approval from the two nations before entering their territorial waters.
Zheng Zhihua, a scholar in marine law from the East China University of Political Science and Law, said rescues in territorial waters were an act that required full sovereignty.
"Foreign vessels have to ask for approval before they enter an area, or come to the area in response to a request by a country," he said.
Zhang Mingliang, a Southeast Asian affairs expert at Jinan University, said Malaysia and Vietnam would likely give approval to the Chinese vessels, even though the Southeast Asian nations were concerned about China's military presence in the region.
"The matter may be complicated and have long-term implications because Malaysia and Vietnam are worried about having Chinese military vessels around them," he said.
The incident showed the need for the claimant states in the South China Sea to formulate a humanitarian rescue co-operation mechanism, he added.
Tang Siew Mun, from Malaysia's Institute of Strategic and International Studies, said the Chinese military vessels could improve the odds of finding the missing plane.
"The fact that China's expanding military power can also have a positive effect is often overlooked and underappreciated," he said.