South Korea and the United States began their largest joint military drills in years on Monday with a resumption of field training, officials said, as the allies seek to tighten readiness over North Korea’s potential weapons tests.

The annual summertime exercises, renamed Ulchi Freedom Shield this year and scheduled to end on Sept. 1, came after South Korean President Yoon Suk-yeol, who took office in May, vowed to “normalise” the combined exercises and boost deterrence against the North.

South Korea separately launched the four-day Ulchi civil defence drills on Monday, designed to boost government readiness, for the first time since the coronavirus pandemic emerged.

The military and civil exercises are aimed at improving the country's preparedness to match the changing patterns of war, with evolving cyber threats against key facilities such as chip factories and supply chains, Yoon said.

“Maintaining peace on the Korean peninsula is built on our airtight security posture,” Yoon told a cabinet meeting, calling for thorough exercises based on real-world scenarios.

The drills were the largest since 2017 after being scaled back because of covid-19 and as Yoon's predecessor sought to restart talks with Pyongyang, which has called the exercises a rehearsal for invasion.

North Korea fired two cruise missiles from the west coast last week, after South Korea and the United States kicked off preliminary training for the exercises.

North Korea has conducted missile tests at an unprecedented pace this year and is ready to conduct its seventh nuclear test at any time, Seoul officials said.

Yoon has said his government is willing to provide economic aid if Pyongyang takes steps toward denuclearisation, but North Korea has rebuffed his offer, openly criticising him.

Seoul’s defence ministry has said the allies would stage 11 field training programmes, including one at brigade-level - involving thousands of soldiers - this summer.

To better counter North Korea’s growing missile threats targeting the South’s capital, the ministry said it would improve missile detection capabilities and push for an early deployment of a new interceptor system.

The United States, South Korea and Japan participated in a recent ballistic missile defence exercise off Hawaii’s coast, the first such drills since 2017, when relations between Seoul and Tokyo hit their lowest point in years.