"South Korea is closely monitoring the situation under the collaboration with the U.S.", said Lee Eugene, vice ministry spokesperson at a regular press briefing.
The officials told Fox News that the latest engine test on Thursday was conducted in the city of Yun Song, where previous rocket tests have taken place.
Rocket engines are easily re-purposed for use in missiles.
This photo carried by North Korea's state news agency on March 19, 2017, shows the North's ground test of a new high-thrust rocket engine.
USA officials have warned that North Korea is on the path to successfully developing an ICMB capable of hitting the United States unless something changes.
Democrats win annual baseball game with special meaning
Aguilar plays outfield for the Democratic team; before the shooting, Scalise was slated to play second base for the Republicans . Capitol Police checked bags with dogs in tow, in an atmosphere that attendees said seemed particularly alert.
May 31, the USA military held exercises to repel attacks of Intercontinental ballistic missiles.
The officials said it is not yet clear if the activity indicates a sixth nuclear test is imminent, but noted there is concern that North Korea could set off a test during Wednesday's visit to Washington by top Chinese diplomats and military officials.
China's top diplomat, Yang Jiechi, told Trump in a meeting at the White House that Beijing was willing to "maintain communication and co-ordination" with the United States in an effort to diffuse tension on the Korean peninsula, according to a statement from China's foreign ministry on Friday.
21 may, North Korea conducted a test of a ballistic medium-range missiles.
"China is willing to maintain communication and coordination with relevant parties including the United States to ease tensions on the peninsula", State Councillor Yang Jiechi said, according to the ministry. ICBMs have a minimum range of about 3,400 miles (5,500 km), but some are created to travel 6,200 miles (10,000 km) or farther.
"This test could mean that North Korea has already completed development of the 2nd and third-stage ICBM engines". Pyongyang conducted similar tests in March.