SEOUL, South Korea — North Korea fired a short-range ballistic missile toward its eastern sea on Wednesday, extending a recent barrage of weapons demonstrations including what it described as simulated attacks on South Korean and US targets last week.

Seoul’s Joint Chiefs of Staff said the missile was launched from the western town of Sukchon, north of the capital, Pyongyang, and flew across the country toward waters off the North’s eastern coast.

The launch was also detected by Japan’s military, which said the missile flew about 155 mph at a maximum altitude of 30 mph. The relatively low trajectory seemed to align with the flight characteristics of some of North Korea’s newer short-range weapons designed to evade missile defenses.

Japanese Defense Minister Yasukazu Hamada said the missile landed in waters outside of the country’s exclusive economic zone. He said North Korea’s intensifying testing activity was “significantly heightening” regional tensions and that Japan lodged a protest with the North through their embassies in Beijing.                    

The launch came after North Korea fired dozens of missiles last week in an angry reaction to a massive combined aerial exercise between the United States and South Korea that the North described as an invasion rehearsal.

Earlier Wednesday, South Korea’s military said the recovered debris of one of the North Korean missiles that flew southward last week was determined to be a Soviet-era anti-aircraft weapon that dates back to the 1960s.

The North’s military said on Monday that its launches last week were simulations to “mercilessly” strike key South Korean and US targets such as air bases and operation command systems.

It said those tests included ballistic missiles loaded with dispersion warheads and underground infiltration warheads meant to launch strikes on enemy air bases, ground-to-air missiles designed to “annihilate” enemy aircraft at different altitudes and distances, and strategic cruise missiles that fell off South Korea’s southeastern coast.