The drills, overseen by South Korean President Yoon Suk Yeol, are also being held to mark the 70th anniversary of the alliance between the countries and the 75th anniversary of the founding of the South Korean military, his office said.

A total of 2,500 troops took part in the drills in Pocheon, northeast of Seoul, supported by "cutting-edge" military assets, including South Korean F-35 fighters and K9 self-propelled howitzers and U.S. F-16 jets and Gray Eagle drones.

"The exercises were aimed at checking the ability to conduct combined and joint operations to realise 'peace through strength' through practical manoeuvring and live-fire training under the scenario of a North Korean provocation," Yoon's office said in a statement, describing them as the largest live-fire drills ever held with the United States.

The initial phase of the drills were designed to show a response to North Korea's nuclear and missile threats and a full-scale attack.

Later in the programme, allied troops prepared the ground for a counterattack through air and artillery precision strikes on key targets, in order to "completely destroy the North's military threats," it said.

North Korea unsuccessfully tried to launch a spy satellite late last month, in its first such attempt since 2016, with the rocket booster and payload plunging into the sea.

Seoul and Washington condemned the launch as a grave provocation and violation of U.N. Security Council resolutions banning the North's use of ballistic missile technology.

Pyongyang said it was exercising its right to space development and vowed to stage another launch soon to boost its surveillance capabilities against U.S. and South Korean threats.

The isolated North has previously reacted angrily to the allies' military drills, calling them a rehearsal for its invasion.

The United States has about 28,500 troops in South Korea.