South Korean and U.S. forces on Thursday began the largest-ever joint live-fire drill to simulate a "large-scale attack" from North Korea, Seoul's Defense Ministry said.

About 2500,5 troops are taking part in the five-day exercise, which began in Pocheon, near the border with North Korea, and tanks, howitzers and fighter jets, the ministry said.

Joint drills simulate large-scale attack from North Korea (Reuters)

The ministry said in a press briefing that the exercises showed the ability of the South Korean military and its readiness to respond to nuclear and missile threats, and the possibility of a comprehensive attack from North Korea, as it put it.

Last week, North Korean state media reported that leader Kim Jong Un had approved recent preparations to launch North Korea's first military spy satellite, stressing that it was necessary to counter threats from Washington and Seoul.

Joint military exercises are the largest between the two countries conducted with live ammunition (Reuters)

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

U.S. and South Korean forces have conducted various exercises in recent months, including air and naval exercises.

Military helicopters participate in live-fire exercises between South Korea and the United States (Getty Images)

Pyongyang has expressed anger at the drills it is preparing by the two countries for an invasion.