SEOUL (Reuters) - Construction trucks moved into a South Korean base housing a U.S. anti-missile system on Monday, infuriating villagers opposed to its deployment, two days after North Korea vowed to suspend nuclear tests and ahead of a North-South summit.

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Thousands of riot police moved in to disperse the protesters who tried to keep supplies from reaching the site of the Terminal High Altitude Area Defense (THAAD) system in the southern city of Seongju, just days before the first North-South summit since 2007.

“A peace treaty is being discussed... There is no more North Korea (nuclear threat) as an excuse (for deployment of THAAD). We can neither understand nor accept construction plans to operate the THAAD,” the THAAD residents’ committee said in a statement.

The system is aimed at defending against an attack by North Korea which has been pursuing nuclear and missile programmes in defiance of U.N. Security Council resolutions, prompting threats of war from both the North and the United States.

But tensions have eased in recent months, with the North participating in the Winter Olympics in the South and a summit planned between North and South this week and between the North and the United States in May or June.

Residents have been blocking the only road to the site since mid-2017, forcing the U.S. military to use helicopters to shuttle in fuel, food and other supplies. The government’s move on Monday to bring in trucks sparked fierce opposition.

The planned construction at the base is aimed at improving power supplies and accommodation for U.S. and South Korean troops stationed there.

Thousands of riot police were dispatched to remove about 200 protesters, Yonhap News Agency said. Dozens were seen tussling with police, yelling and demanding ambulances be called, live footage through Facebook showed.

“It is imperative to improve living conditions of troops based in Seongju city. We can no longer delay this so the ministry started deploying workers, materials and equipment needed for the construction today,” a Defence Ministry official said.

THAAD, designed to shoot down short- to medium-range missiles, has also angered China which believes the system’s radar could be used to penetrate its territory.

North Korea said on Saturday it would halt nuclear and missile tests and said it was scrapping its Punggye-ri test site to pursue economic growth and peace.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un will hold their summit on Friday.