SEOUL — North Korea on Sunday carried out what appeared to be its boldest ballistic missile test in years, pressing ahead with its recent flurry of launches despite American warnings that the country could be subjected to more sanctions.

The missile was launched from the North Korean province of Jagang, which borders China, and flew across the North before falling into the sea off the country’s east coast, the South Korean military said. It was the North’s seventh missile test this month.

The office of President Moon Jae-in of South Korea said the projectile was an intermediate-range ballistic missile. Flight data suggested that it was the North’s most powerful launch since its last test of an intercontinental ballistic missile, in November 2017. It was fired at a steep angle, reaching an altitude of 1,242 miles while covering a distance of 497 miles, South Korean defense officials said.

When North Korea tests intermediate- and long-range missiles, it usually launches them at a deliberately steep angle to ensure that they don’t fly over Japan, which would be considered extremely provocative by Tokyo, Washington and their allies. Such missiles could cover much more distance if they were launched at normal ballistic missile trajectories.

In the North’s last ICBM test in 2017, the missile reached an altitude of 2,796 miles and covered a distance of 596 miles. After that test, North Korea claimed that its ballistic missiles could target parts or all of the continental United States with nuclear warheads.

The missile test Sunday was North Korea’s third in the last week and its seventh in January, which appears to have been its busiest month for missile launches since Kim Jong-un, its leader, came to power a decade ago. Until now, North Korea had never test-launched more than six missiles a month under Mr. Kim, according to South Korea’s national news agency, Yonhap.

Mr. Kim has vowed to concentrate on expanding the North’s nuclear and missile capabilities since his diplomacy with then-President Donald J. Trump ended without an agreement in 2019. He has rebuffed the Biden administration’s repeated offers to resume talks “without preconditions”; instead, he has ordered his government to prepare for a “long-term confrontation” with the United States.

The new spate of missile tests has surprised some analysts in the region, who had expected the North to refrain from raising tensions before the Winter Olympics in Beijing, which begin this week. China is the North’s only major ally.

The United States’ worsening relations with China and Russia appear to have given Mr. Kim an opening to test weapons with impunity. When Washington asked the United Nations Security Council to impose more sanctions on North Korea for its recent ballistic missile tests, which violated the council’s resolutions, both Beijing and Moscow vetoed the move.

In its last two weapons tests, North Korea said it flight-tested two long-range cruise missiles and a tactical guided missile that outside analysts call KN-23. The KN-23 is a short-range ballistic missile designed to thwart missile defense systems by making low-altitude, mid-flight maneuvers, according to missile experts.

On Friday, North Korea’s state media said Mr. Kim had visited “a munitions factory producing a major weapon system” to encourage his weapons developers.

In late 2019, Mr. Kim warned that he no longer felt bound by his self-imposed moratorium on nuclear and long-range missile tests. ​ During a Politburo meeting last ​week, he ​again ​suggested that his government might resume its testing of long-range missiles and nuclear devices​.