"The ballistic missiles' flight went from 500 km to 600 km, which is a distance far enough to strike all of South Korea, including Busan," the South's military said in a statement.
Busan is a South Korean port city in the south.
North Korea has test-fired a series of ballistic missiles in recent months, in defiance of U.N. Security Council resolutions, including intermediate-range missiles in June and a submarine-launched missile this month.
"In addition to the basic goal of enhancing missile units' readiness to fight, it might be a way of reminding their southern neighbors that the site chosen for a THAAD battery in South Korea is within reach," Joshua Pollack, editor of the U.S.-based Nonproliferation Review, said of Tuesday's launches.
South Korea announced last week the THAAD system would be deployed in the southeastern county of Seongju.
In addition to the decision to base a THAAD system in South Korea, the United States recently angered North Korea by blacklisting its leader Kim Jong Un for human rights abuses.
"The threat to our national security is growing very quickly in a short period of time," South Korean Prime Minister Hwang Kyo-ahn told parliament on Tuesday.
Bombs, missiles and sanctions
North Korea conducted its fourth test of a nuclear device in January, and activity at its nuclear test site has increased recently, according to media reports in South Korea and Japan citing government officials, as well as a report by Washington-based North Korea monitoring project 38 North.
Following the latest nuclear test and a February space rocket launch that was widely viewed as a missile test in disguise, the U.N. Security Council imposed tough new resolutions that further isolate North Korea.
While China supported tougher sanctions against its neighbor and ally North Korea, it has sharply criticized the decision to base a THAAD battery in South Korea, saying the move would destabilize the security balance in the region.
"The situation on the Korean peninsula is severe and complex and all sides should avoid any actions that raise tensions," China's foreign ministry said, echoing previous statements.
Japan denounced the launches.
"The latest launch is a breach of the UN Security Council resolution and is extremely hazardous to shipping and aircraft and we have strongly protested," the Japanese government said in a statement.