U.S. missile launchers and other equipment needed to set up a controversial missile defense system have arrived in South Korea, the U.S. and South Korean militaries said Tuesday, a day after North Korea test-fired four ballistic missiles into the ocean near Japan.

The plans to deploy the Terminal High-Altitude Area Defense system, or THAAD, within this year have angered not only North Korea, but also 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.

“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.”

China’s condemnation of South Korean plans to deploy THAAD has triggered protests against a South Korean hypermarket chain, Lotte Mart, whose parent company agreed to provide one of its golf courses in southern South Korea as the site of THAAD. Visits by South Korean film stars and singers have been canceled and shipments of South Korean cosmetics have been held up at customs.

Experts say China could also send Chinese coast guard ships to escort fishing boats into waters claimed by South Korea, dispatch military aircraft and ships into South Korean air and sea space, and suggest that it might do less to restrain North Korea from provocative behavior.

Russia has supported China’s opposition to the system. Militarily, Russia and China could deploy more missiles, especially those with maneuverable warheads to overwhelm THAAD, along with the use of decoys and attempts to jam the system, analysts say.

On Tuesday, China’s Global Times, an outspoken nationalist 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.”

An official from South Korea’s Defense Ministry, who didn’t want to be named, citing office rules, said the equipment that arrived in South Korea included launchers, but didn’t confirm how many.

While South Korean media speculate that the THAAD deployment could be completed as early as April, the ministry official couldn’t confirm those reports. The official said the plan was to have the system operational as soon as possible.

On Monday, North Korea fired four ballistic missiles in an apparent protest against ongoing U.S.-South Korean military drills that it views as an invasion rehearsal. The missiles flew about 1,000 kilometers (620 miles) on average, three of them landing in waters that Japan claims as its exclusive economic zone, according to South Korean and Japanese officials.

The North’s state media on Tuesday said leader Kim Jong Un supervised a ballistic rocket launching drill, a likely reference to the four launches reported by Seoul and Tokyo. Involved in the drills were artillery units tasked with striking “U.S. imperialist aggressor forces in Japan,” according to the Korean Central News Agency.

There was pride and defiance among the elite citizens who live in North Korea’s showcase capital, Pyongyang.

“If the U.S. imperialists and their South Korean puppets shoot even just one spark into our sovereign territory, we will completely destroy those aggressors, without any mercy, with our invincible Hwasong artillery, which are loaded with nuclear warheads,” Sim Chol Su, echoing the propaganda often found in state media, told The Associated Press.

North Korea uses “Hwasong” to describe a broad range of its ballistic missiles, including Scuds and the mid-range missiles that are referred to as Rodong and Musudan by outside analysts.

South Korea’s Joint Chiefs of Staff said the missiles fired by the North were believed to be “improved versions” of Scud missiles. South Korean experts say North Korea’s extended-range Scuds and mid-range Rodong missiles are capable of hitting Japan, including U.S. military bases in Okinawa.

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,” a KCNA dispatch said.

(AP)