South Korea and the United States began their joint springtime military exercises Monday, the South Korean military said, amid strong protests from North Korea.

According to South Korea's Joint Chiefs of Staff, the nine-day exercises will be computer simulated and not involve field drills.

"The training this time will offer a chance to enhance the combined operational capabilities of South Korean and U.S. troops and further solidify the allies' combined defense posture," the JCS said in a statement.

North Korea harshly criticized the exercises on its state-run propaganda website Uriminzokkiri on Sunday, saying, "Invaders and provocateurs must pay" for their actions.

The country on Saturday fired a new type of missile that reached an altitude of about 25 kilometers and flew about 110 km, South Korea's JCS said on Sunday.

Sung Kim, U.S. special representative for North Korean affairs, arrived in Seoul on Sunday for a five-day trip and is slated to meet with his South Korean counterpart Noh Kyu-duk later in the day.

Concerns are growing about further North Korean provocations around the 90th anniversary of the founding of the Korean People's Revolutionary Army on April 25.