Vietnam has discreetly fortified several of its islands in the disputed South China Sea with new mobile rocket launchers capable of striking China's runways and military installations across the vital trade route, according to Western officials.
Diplomats and military officers told Reuters that intelligence shows Hanoi has shipped the launchers from the Vietnamese mainland into position on five bases in the Spratly islands in recent months, a move likely to raise tensions with Beijing.
The launchers have been hidden from aerial surveillance and they have yet to be armed, but could be made operational with rocket artillery rounds within two or three days, according to the three sources.
Vietnam's Foreign Ministry said the information was "inaccurate", without elaborating.
Deputy Defence Minister, Senior Lieutenant-General Nguyen Chi Vinh, told Reuters in Singapore in June that Hanoi had no such launchers or weapons ready in the Spratlys but reserved the right to take any such measures.
"It is within our legitimate right to self-defense to move any of our weapons to any area at any time within our sovereign territory," he said.
The move is designed to counter China's build-up on its seven reclaimed islands in the Spratlys archipelago. Vietnam's military strategists fear the building runways, radars and other military installations on those holdings have left Vietnam's southern and island defenses increasingly vulnerable.
Military analysts say it is the most significant defensive move Vietnam has made on its holdings in the South China Sea in decades.