North Korea fired several short-range missiles early Saturday off its east coast, officials in South Korea said, indicating a possible resumption of sabre-rattling by the North after a nearly month-long hiatus.

The launches took place amid an annual joint military exercise between South Korea and the United States. While the allies say the training is defensive in nature, the North has condemned it as a rehearsal for an invasion.

The South Korean military's Joint Chiefs of Staff said the North fired "several unidentified projectiles" from the vicinity of Gitdaeryong in its eastern province of Gangwon starting at around 6:49 a.m.

The projectiles flew more than 250 kilometers in a northeastern direction, it added.

The presidential office said that the projectiles are believed to be artillery rockets from a multiple-rocket launcher.

The U.S. Pacific Command in Hawaii said the North fired three short-range ballistic missiles between 6:49 a.m. and 7:19 a.m., of which two flew approximately 250 km in a northeastern direction.

The command added that the missiles did not pose a threat to North America or Guam, which the North earlier this month threatened with a missile strike.

In its earlier assessment soon after the test, it said the first and third missiles failed in flight and the second blew up "almost immediately."

U.N. resolutions ban North Korea from any use of ballistic missile technology, while short-range missile launches are not prohibited.

According to Yonhap News Agency, the presidential office said in a statement following a National Security Council meeting that officials decided to proceed "more thoroughly" with the South Korea-U.S. combined military drill that kicked off Monday.

In Tokyo, Defense Minister Itsunori Onodera told reporters he believes North Korea fired "multiple short-range ballistic missiles or rockets," indicating the difficulty in determining whether the missiles were ballistic.

Meanwhile, Chief Cabinet Secretary Yoshihide Suga said the missiles did not fall within Japan's territory or exclusive economic zone and would not have a direct impact on Japan's security.

The Japanese government top spokesman also explained that Prime Minster Shinzo Abe instructed him to maintain high levels of alert to "protect the lives and property of the Japanese people."

A Japanese government source said the launches appeared to have been conducted as part of drill by the North Korean military.

In Washington, the White House said U.S. President Donald Trump was briefed on the launches and that the administration is monitoring the situation.

Tensions remain high in the region as North Korea said earlier this month it was considering launching ballistic missiles over the Japanese archipelago into waters near Guam, a U.S. territory in the western Pacific.

Prior to Saturday, the most recent missile launch by North Korea was on July 28, when it test-fired a Hwasong-14 intercontinental ballistic missile, the second such test that month.

The hiatus prompted U.S. Secretary of State Rex Tillerson this week to hail Pyongyang's restraint with its weapons programs.

The two ICBM launches prompted the U.N. Security Council to impose fresh sanctions on Pyongyang that aim to slash the country's $3 billion annual export revenue by a third.

The United States, Japan and South Korea have been on heightened alert against possible provocative acts by the North as Friday marked the anniversary of its "Songun" (military-first) policy.

Last year, Pyongyang fired a submarine-launched ballistic missile on Aug. 24, a day before the anniversary, and went on to carry out its fifth nuclear test on Sept. 9, the country's founding day.