SEOUL: South Korean and U.S. forces began their largest-ever joint live-fire exercises on Thursday, simulating a "full-scale attack" from North Korea, South Korea's defence ministry said.

Some 2,500 troops from the South and the United States took part as the five-day exercise began in Pocheon near the border with the North, the ministry said. Multiple tanks, howitzers and fighter jets were also involved, it said.

"The exercise demonstrated our military's capability and readiness to strongly respond to North Korea's nuclear and missile threats and to a full-scale attack," the ministry said in a news release.

Last week, North Korea's state media reported that leader Kim Jong Un had approved final preparations for the launch of the North's first military spy satellite. Kim has said it is necessary to counter threats from the U.S. and South Korea.

Analysts say the satellite will improve North Korea's surveillance capability, enabling it to strike targets more accurately in the event of war.

Recent commercial satellite imagery showed progress on a new launch pad in the North's satellite launching station, with activity at a "new level of urgency," most likely in preparation for the launch, the U.S.-based monitoring group 38 North said.

U.S. and South Korean forces have been carrying out various training in recent months, including air and sea drills involving U.S. B-1B bombers, after hopes for diplomatic efforts and COVID-19 restrictions led to many drills being scaled back.

North Korea has reacted angrily to the drills, which it sees as preparation by U.S. and South Korean forces for an invasion.