U.S. Forces Korea and South Korean military have delivered new interceptor missiles onto Terminal High Altitude Area Defense (THAAD) base in Seongju despite local residents protests.

South Korea and the United States military brought equipment and vehicles of THAAD missile defense system and other items into an American military base Friday in a surprise overnight operation aimed at skirting opposition from local residents.

According to Yonhap, the Korean Defense Ministry said it has supported the ground transportation of the replacement missiles, as well as power generators and electronic equipment for data collection, and other supplies to improve living conditions of military officials on a Terminal High Altitude Area Defense base in Seongju, North Gyeongsang Province.

The delivery began late Thursday evening and ended at around 6 a.m. Friday morning, according to the ministry.

“The new missiles are the same type and quantity as the previous one,” a ministry official said stressing the current ones reached the end of their operating cycle. The ministry, however, declined to give out the exact number.

On concerns that the latest transport is part of US’ announced plan to enhance performance of its seven THAAD batteries deployed around the world, with one in South Korea, the official stressed it has nothing to do with the upgrade.

“No additional THAAD launchers have entered South Korea or the base,” the official added.

The U.S. has installed the THAAD system in Seongju, with a total of six launchers, since 2017 to counter North Korea’s missile threat. There are eight interceptor missiles for each launcher, putting the total number of missiles in South Korea at 48.

The construction to improve residential facilities for the troops began in August last year.

A ministry official said the ground transport was inevitable to move some hardware, and the government had discussions with local residents regarding the matter several times but failed to win their full consent.

No major conflicts with the residents there have been reported so far, he added.

The THAAD deployment has been one of the most sensitive issues for South Korea, as China has taken economic retaliatory measures for Seoul’s hosting of the battery. Seoul and Washington have stressed that the system aims only to better cope with the growing missile threats posed by North Korea.