South Korea has conducted a missile drill simulating an attack on the North Korean nuclear site, in response to Pyongyang's sixth test.
The live-fire exercise saw rockets launched from fighter jets and ballistic missiles from the ground.
It came as the US warned that any threat to itself or its allies would be met with a "massive military response".
The North says it tested a hydrogen bomb that can fit on a long-range missile.
Pyongyang has repeatedly defied UN sanctions and international pressure by developing nuclear weapons and testing missiles, and the provocations have only intensified.
In the past two months it has conducted intercontinental ballistic missile tests, sending one over mainland Japan into the Pacific Ocean. It has also threatened to fire missiles towards the US Pacific territory of Guam.