BEIJING (Reuters) - China’s Defence Ministry confirmed on Thursday that it was pressing ahead with anti-missile system tests after pictures appeared on state television, amid anger at South Korea’s decision to deploy an advanced U.S. anti-missile system.

An announcement by South Korea and the United States this month that they would deploy a Terminal High Altitude Area Defence (THAAD) unit has drawn protests from China, which warned that the system would destabilize regional security.

The decision by the United States and South Korea is the latest move to squeeze increasingly isolated North Korea, but China worries the system’s radar will be able to track its military capabilities. Russia also opposes the deployment.

Pictures broadcast this week on Chinese television were the third time since 2010 that China has publicly indicated tests of its own anti-missile system, state media said.

“To develop suitable capabilities for missile defense is necessary for China to maintain its national security,” Defence Ministry spokesman Yang Yujun told a regular monthly briefing, when asked about the footage.

“It will improve the self-defense capability of China and is not targeting any specific country and will not affect international strategic stability,” he added, without elaborating.

South Korea and the United States have said THAAD would only be used in defense against North Korean ballistic missiles and they have tried to assuage Chinese concerns, without apparent success.

A senior U.S. administration official said on Tuesday, at the end of a visit to China by U.S. National Security Adviser Susan Rice, that the decision to deploy THAAD did not threaten China’s security.

Yang repeated that China would consider taking unspecified measures to maintain strategic balance, and dismissed assertions that THAAD was no threat to China.

“As for the technical excuses from the United States and South Korea, experts can easily see how believable this is,” he said.

North Korea has launched a series of missiles in recent months, the latest last week when it fired three ballistic missiles in what it said was a simulated test of preemptive strikes against South Korean ports and air fields used by the U.S. military.

China’s military is undergoing an ambitious modernization program that has included tests of anti-satellite missiles.