The Joint Chiefs of Staff of South Korea announced Tuesday that North Korea fired an unidentified projectile into the sea off its east coast, which they believe was a ballistic missile. The projectile was launched at 7:27 a.m. local time Tuesday (5:27 p.m. ET Monday), according to the military, which is keeping a "readiness posture" in case more launches are needed. According to the statement, the military is closely monitoring relevant movements with close collaboration from the US. By 7:45 a.m. local time, the "possible ballistic missile" had most certainly fallen into the sea, according to Japan's Coast Guard. It urged all vessels not to approach the stricken item and to report any sightings to the authorities. In a statement, the South Korean government "expressed a strong regret over the North's launch, which took place at a time when political stability is very important." North Korea launched its second projectile in less than a week on Tuesday. According to South Korea's Joint Chiefs of Staff, North Korea fired an unidentified projectile into waters off the east coast of the Korean Peninsula on Wednesday. North Korea claims to be testing a hypersonic missile, the government of Kim Jong Un's second claimed test of such a weapon. Many experts, however, questioned this assertion. According to Japan's Defense Ministry, Tuesday's test reached roughly the same distance as last week's, 700 kilometres (435 miles), and the missile fell into the sea outside of Japan's Exclusive Economic Zone (EEZ). North Korea has not released any details regarding the launch on Tuesday. North Korean official media released details 24 hours after the test last week. International law prohibits Pyongyang from testing ballistic missiles and nuclear weapons.