North Korea fired its fourth short-range missile in the past two days into waters off its east coast on Sunday, despite calls for restraint from South Korea and other countries in the region, as well as the United Nations.

The latest launch into the Sea of Japan, confirmed by South Korean Defense Ministry officials, follows three coastal launches on Saturday that rattled the region.

North Korea routinely tests short-range missiles into coastal waters. But the latest launches, which analysts say may have included rockets from a new multiple launcher, come at a time of heightened North-South tensions. Since March, Pyongyang has repeatedly threatened to attack South Korea and threatened the United States with nuclear strikes.

A South Korean defense official said Saturday the North's intentions with the launches were not clear. He said South Korea's military was watching for any additional launches or other provocations.

The United States, Russia and the United Nations have all issued renewed calls for restraint from North Korea. A spokesman for South Korea's Unification Ministry called the latest weapons tests a "deplorable" provocation.