North Korea launched two ballistic missiles toward its east coast early Monday morning, according to South Korea’s Joint Chiefs of Staff (JCS), assessing that one may have failed in flight.

It follows Pyongyang’s claim that it tested an advanced multiple warhead missile last Wednesday, which Seoul disputed and called a failure, and as leader Kim Jong Un kicked off a major party plenum over the weekend.

JCS said North Korea fired one short-range ballistic missile (SRBM) at 5:05 a.m. KST toward the northeast from the Jangyon area of South Hwanghae Province on the southwest coast, flying around 372 miles