SEOUL, South Korea — China reacted strongly Tuesday to reports that U.S. missile launchers and other equipment needed to set up a controversial missile defense system have arrived in South Korea.

The plans to deploy the Terminal High-Altitude Area Defense system, or THAAD, within this year have angered North Korea, China and Russia, which see the system’s powerful radars as a security threat.

China responded quickly, saying it will take “necessary measures” to protect itself and warning that the U.S. and South Korea should be prepared to bear the consequences.

Washington and Seoul say the system is defensive and not meant to be a threat to Beijing or Moscow. The U.S. military said THAAD can intercept and destroy short and medium-range ballistic missiles during the last part of their flights.

The arrival of the equipment was announced by the U.S. and South Korean militaries Tuesday, a day after North Korea test-fired four ballistic missiles into the sea near Japan.

“Continued provocative actions by North Korea, to include yesterday’s launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea,” Adm. Harry Harris, head of the U.S. Pacific Command, said in a statement.

Some South Korean liberal presidential candidates have said that the security benefits of having THAAD would be curtailed by worsened relations with neighbors China and Russia.

“China firmly opposes the deployment of THAAD,” Chinese Foreign Ministry spokesman Geng Shuang said at a regular briefing Tuesday. “We will definitely be taking necessary measures to safeguard our own security interest. All consequences entailed from that will be borne by the U.S. and (South Korea). We once again strongly urge the relevant sides to stop the process of deployment and refrain from going further down that wrong path.”

State Department acting spokesman Mark Toner said THAAD is a defensive system being put in place because of North Korea’s provocative behavior.

“We have been very clear in our conversations with China that this is not meant to be a threat, and is not a threat to them or any other power in the region,” he said.

On Tuesday, China’s Global Times, a tabloid published by the ruling Communist Party’s flagship People’s Daily, criticized North Korea over its missile tests.

“By firing four missiles at once this time, the military confrontation between Pyongyang, Seoul and Washington escalates a notch,” the newspaper said. “Noticeably, the Chinese public is angry that Pyongyang’s nuclear program has provided an excuse for Seoul to deploy THAAD.”

Kim “ordered the KPA (Korean People’s Army) Strategic Force to keep highly alert as required by the grim situation in which an actual war may break out anytime,” North Korea’s news agency said.