SEOUL — North Korea fired two short-range ballistic missiles off its east coast on Monday, in its fourth weapons test in a month.

The missiles, fired from near the Suan Airport outside Pyongyang, the North’s capital, flew 236 miles to the northeast before landing off the east coast, the South Korean military said.

The test came after the country fired two ballistic missiles from train cars on Friday, hours after it warned of “stronger and certain reaction” if the United States helped impose more sanctions in response to the North’s recent series of missile tests.

​The missile tests have raised tensions at a sensitive time: China ​is preparing to host the Winter Olympics in Beijing next month, and South Korea is gearing up for its presidential election on March 9​​.

North Korea resumed testing missiles in September, after a six-month hiatus. It has since conducted at least six missile tests, which involved a long-range strategic cruise missile, ballistic missiles​ from train cars​ rolled out of mountain tunnels and a submarine-launched ballistic missile.

In two tests​ conducted on Jan. 5 and Jan. 11, it launched what it called hypersonic ballistic missiles with detachable gliding warheads, which made them harder to intercept because they could change course during flight.

​In response, the United States blacklisted five North Korean officials active in China and Russia who American officials said had been involved in procuring goods for the North’s nuclear weapons and missile programs. Washington has also proposed that the U.N. Security Council place fresh sanctions on North Korea​.

Multiple Security Council resolutions ban North Korea from developing or testing ballistic missile technologies or technologies used to make and deliver nuclear weapons. But the North​ insists that when it tests its missiles, it is exercising its “right to self-defense” and that the missile tests are “part of its efforts for modernizing its national defense capability.”

​North Korea launched three intercontinental ballistic missiles in 2017, claiming that it was capable of targeting the continental United States with ​nuclear warheads. Its leader, Kim Jong-un, then started negotiations with President Donald J. Trump. But ​their three meetings ended​ in 2019​ without an agreement on how to roll back the North’s nuclear weapons program or when to lift sanctions.

​North Korea has since resumed testing mostly short-range ballistic missiles, and Mr. Kim has warned that he no longer feels bound by ​his self-imposed moratorium on nuclear and long-range missile tests.