China has deployed anti-frogmen rocket launchers intended to fend off Vietnamese intrusions on one of its man-made islands in the contested South China Sea, Chinese state media reported Wednesday.

The report, published on the Weibo account of the state-run Defense Times newspaper, said China installed Norinco CS/AR-1 55mm rocket defense systems on Fiery Cross Reef in the strategic Spratly chain — just days after the two rivals said they would work to “manage and properly control” their maritime disputes.

The system has the capability to discover, identify and attack enemy combat divers, according to the report. A similar system known as the DP-65 anti-diver grenade launcher was seen on Fiery Cross in 2012, according to IHS Jane’s Defence Weekly.

Fiery Cross is controlled by China but also claimed by the Philippines, Vietnam and Taiwan.

The Defense Times report did not say when exactly the rocket-launcher systems were installed, but alluded to them being a response to soaring tensions between Beijing and Hanoi in 2014 after China sent a massive oil rig to the area near the Paracel Islands, which are also claimed by Vietnam.

The report comes just two days after the rivals said in a joint communique China released Monday that they had agreed to “manage and properly control maritime disputes, not take any actions to complicate the situation or expand the dispute, and maintain peace and stability in the South China Sea.”

Last year, Hanoi lambasted Beijing after reports emerged that China had placed HQ-9 surface-to-air missiles on Woody Island, which is part of the Paracel Islands. Vietnam called the move a serious infringement of its sovereignty over the island chain.

Beijing has stoked concern in regional capitals and with Washington over its massive land-reclamation projects in the disputed South China Sea.

All seven of its man-made islets are in the hotly contested Spratlys, and three of those — including Fiery Cross — boast military-grade airfields.

The U.S. says China has continued to bolster its military capabilities in the South China Sea as it seeks to reinforce effective control of much of the waterway, through which $5 trillion in trade passes each year, despite a 2015 pledge by Chinese President Xi Jinping not to further militarize them.

The Asia Maritime Transparency Initiative, part of the Center for Strategic and International Studies, said in late March that major construction at the three largest of China’s man-made islands in the Spratlys was nearly finished, allowing Beijing to deploy fighter jets and mobile missile launchers to the area at any time.

AMTI said all three islands boast hangers that can accommodate 24 fighter jets and four larger planes, including surveillance, transport, refueling or bomber aircraft. Hardened shelters with retractable roofs for mobile missile launchers have also been built on the islands.

China has also constructed significant radar and sensor arrays on all three islets, positioning them close to point defense structures to provide protection against air or missile strikes.