China upgraded the missile system of its only Luhai-class destroyer Shenzhen, which will resume operations with the People’s Liberation Army Navy’s fleet in the South China Sea. The move comes at a time when tensions continue to mount in the disputed region.

Shenzhen’s missile system was upgraded to a 32-cell vertical launch to fire medium-range HHQ-16 surface-to-air missiles, according to a report by IHS Jane’s 360, a British publishing company that keeps records on military equipment, on Wednesday. HHQ-16 SAM system is reported to have a range of 19 nautical miles and a maximum speed of 2,148 miles per hour. According to defense experts, it is comparable to the Russian Gollum/Shtil-2 missile system.

Four 37 mm twin anti-aircraft guns have also been replaced with two Type 1130 close-in weapon systems along with upgraded surface and air search radars. Shenzhen’s radar system has also been improved to take out a blind spot in the previous system’s visible range.

The 6,000-ton destroyer was commissioned in 1999, and it is exclusive among modern destroyer classes due to its steam propulsion system. Shenzhen also works as a helicopter hangar and has space for the landing and takeoff of up to two helicopters.

The development comes nearly a month after the Permanent Court of Arbitration in the Hague ruled that China’s unreserved claims in the South China Sea are illegal and not based on any historic claims. In response, Beijing rejected the court’s ruling with Chinese President Xi Jinping saying the South China Sea islands have been “Chinese territories since ancient times.” Russia supported China’s rejection of the court ruling.

The South China Sea region has been long contested, with Brunei, China, Malaysia, the Philippines, Taiwan and Vietnam laying claim to various areas. Beijing has been expanding its presence in the disputed region and has built three runways on the Spratly archipelago. However, China has consistently defended its actions, saying it does not have any intentions of starting a conflict and that its aircraft facilities will maintain safety in the region.