North Korea fires projectiles, marking the 4th launch in the last 2 weeks The test comes as the U.S. and South Korea began joint military exercises.

For the fourth time in less than two weeks, North Korea has fired missiles into the Sea of Japan, a U.S. official said.

The two missiles, fired on Tuesday morning local time, were assessed to be similar to the short-range ballistic missiles tested by North Korea last week, the official said. In a statement, the South Korean Joint Chiefs said the missiles flew approximately 280 miles.

"We continue to monitor the situation and are consulting closely with our South Korean and Japanese allies," a senior U.S. administration official told ABC News in a statement.

The latest test comes as U.S. Defense Secretary Mark Esper is in the region for meetings this week with his Japanese and South Korean counterparts and the U.S. and South Korea began joint military exercises on the Korean peninsula.

A spokesperson for North Korea's Foreign Ministry decried the exercises, which are computer-based and have been scaled down in size from previous years, as "an undisguised and a flagrant violation" of agreements between the U.S. and North Korea.

"Although the U.S. and South Korean authorities are playing all sorts of tricks to justify the joint military exercise, its aggressive nature can neither be covered up nor whitewashed in any manner," the spokesperson said on Tuesday.

Esper told reporters traveling with him to Japan on Tuesday that there is no plan to scale back future military exercises "at this point," reiterating that the computer-based exercise was adjusted "in order to open the door for diplomacy."

In March, the U.S. and South Korea announced the conclusion of its large spring military exercise in support of diplomatic efforts to denuclearize North Korea. That annual exercise was routinely protested by Pyongyang as provocative. Instead, the U.S. has been holding new exercises at lower command levels to allow both U.S. and South Korean forces to maintain their readiness — though possibly not at the same levels as if the larger exercises had been held.

Esper said the U.S. takes North Korean missile launches seriously but needs to be "careful not to overreact and not to get ourselves in a situation where diplomacy is closed off."

"While we take these launches seriously, we monitor them. We try to understand what they’re doing and why," Esper said. "We also need to be careful not to overreact and not to get ourselves in a situation where diplomacy is closed off. And so I know the State Department continues to engage, and we’re looking forward to the next round of working level talks [between the U.S. and North Korea] sooner rather than later."

Last Thursday, North Korea launched at least one short-range ballistic missile into the Sea of Japan, assessed to be similar to the missiles tested earlier that week.

President Donald Trump downplayed that launch, saying, "Short-range missiles, we never made an agreement on that. I have no problem. We'll see what happens. But these are short-range missiles. They are very standard."