An advanced U.S. missile defense system will be deployed in a rural farming town in southeastern South Korea, Seoul officials announced Wednesday, angering not only North Korea and China but also local residents who fear potential health hazards that they believe the U.S. system might cause.

As words of the location for the Terminal High-Altitude Area Defense, or THAAD, spread even before the government's formal announcement, thousands of residents in the town of Seongju, the site for the U.S. system, rallied and demanded the government cancel its decision. A group of local leaders wrote letters of complaint in blood that they plan to give to the Defense Ministry.

"We oppose with our lives the THAAD deployment," one of the letters said, according to Seongju local council speaker Bae Jae Man, one of the 10 people who wrote the letter.

Seoul and Washington officials say they need the missile system to better deal with what they call increasing North Korean military threats. On Monday, North Korea warned it will take unspecified "physical" measures once the location for THAAD is announced.

Seoul's Deputy Defense Minister Ryu Je Seung told a news conference that Seongju was picked because it can maximize the THAAD's military effectiveness while satisfying environmental, health and safety standards.

Ryu said a THAAD system stationed in Seongju would cover two-thirds of South Korea's territory from possible North Korean nuclear and missile threats. He said the defense chiefs of the countries approved the decision.

China and Russia oppose the system that they believe helps U.S. radar track missiles in their countries. Seoul and Washington say the system targets only North Korea. Many South Koreans worry China, South Korea's biggest trading partner, might take economic retaliatory measures.

Residents in Seongju and several other villages previously rumored to be candidate sites for the THAAD system have already launched protests, citing fears that the electromagnetic waves that THAAD radar systems emit can possibly cause health problems.

Defense officials have disputed that, saying the system will be located on a mountain, not in a residential area, and is harmless if people stay at least 100 meters (yards) away from it.

Seoul and Washington launched talks on the THAAD deployment after North Korea conducted a fourth nuclear test and carried about a long-range rocket launch earlier this year.

The United States stations about 28,500 troops in South Korea as deterrence against potential aggression from North Korea. China assisted North Korea during the 1950-53 Korean War, while American-led U.N. troops fought alongside South Korea.