Seoul, South Korea — South Korea's military said North Korea on Thursday fired two projectiles toward its eastern sea, an apparent resumption of weapons tests aimed at ramping up pressure on Washington over a stalemate in nuclear negotiations.

Seoul's Joint Chiefs of Staff said the weapons were fired from a region near the North Korean capital of Pyongyang. The Joint Chiefs didn't immediately confirm whether the weapons were ballistic missiles or rocket artillery, or how far they flew.

The Pentagon told CBS News they appeared to be missiles. Japan's coast guard said the same thing, adding that they landed in the sea between the Korean peninsula and Japan, according to the Reuters news agency.

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The South Korean Joint Chiefs told CBS News the South's military "is maintaining its readiness posture while keeping track of related movements in preparation for further launches."

North Korea's latest launch follows statements of displeasure by top government officials over the slow pace of nuclear negotiations with the United States and demands that the Trump administration ease sanctions and pressure on Pyongyang.

Senior North Korean official Kim Yong Chol on Sunday said his country was running out of patience with Washington over what it described as unilateral disarmament demands, and warned that a close personal relationship between the leaders alone wouldn't be enough to prevent nuclear diplomacy from derailing.

He said the Trump administration would be "seriously mistaken" if it ignores an end-of-year deadline set by North Korean leader Kim Jong Un for mutually acceptable terms for a deal to salvage nuclear diplomacy.

Nam Sung-wook, a North Korea expert at Seoul's Korea University, said North Korea will likely ramp up its weapons demonstrations in coming weeks to increase pressure on Washington ahead of Kim's deadline. There's a possibility that the North would fire some of its powerful mid-range missiles over Japan, as it did during a provocative run in weapons tests in 2017, Nam said.

"North Korea is investing all its strength in a hard-line position against Washington and Seoul," said Nam, a former president of the Institute for National Security Strategy, a think tank affiliated with South Korea's main spy agency. "If its missiles fly over Japan, the international impact would be huge because the United States and Japan would find it difficult to let it go," he said.

Earlier this month, the North test-fired an underwater-launched ballistic missile for the first time in three years. The North has also tested new short-range ballistic missile and rocket artillery systems in recent months in what experts saw as an effort to use the standstill in talks to advance its military capabilities while increasing its bargaining power.

Negotiations have faltered after the collapse of a February summit between Kim Jong Un and Trump in Hanoi, Vietnam, where the U.S. rejected North Korean demands for broad sanctions relief in exchange for a piecemeal deal toward partially surrendering its nuclear capabilities.

The North responded with intensified testing activity while Kim said he would "wait with patience until the end of the year for the United States to come up with a courageous decision."

Washington and Pyongyang resumed working-level discussion in Sweden earlier this month, but the meeting broke down amid acrimony with the North Koreans calling the talks "sickening" and accusing the Americans of maintaining an "old stance and attitude."

After the breakdown in Sweden, North Korea released a series of photos showing Kim riding a white horse to a snow-covered Mount Paektu, a volcano considered sacred by North Koreans and a place where the leader has often visited before making key decisions. Speaking to officials near the mountain, Kim vowed to overcome U.S.-led sanctions that he said had both pained and infuriated his people.

News of the launches came after South Korea said earlier Thursday that North Korean leader Kim Jong Un sent a message of condolence to South Korean President Moon Jae-in over his mother's recent death. The two leaders met three times last year and struck a set of deals aimed at easing animosities and boosting exchanges. But in recent months, the North has drastically reduced its engagement and diplomatic activities with South Korea, after Seoul failed to resume lucrative joint economic projects held back by U.S.-led U.N. sanctions.

Last week, Kim ordered the destruction of South Korean-built facilities at a long-shuttered joint tourist project at North Korea's scenic Diamond Mountain resort. South Korea later proposed talks but North Korea has insisted they exchange documents to work out details of Kim's order.

"The North Korean leader does not ride a white horse to the top of Paektu mountain because he is satisfied with the status quo," said Leif-Eric Easley, a professor at Ewha University in Seoul.

"Kim's year-end threat is as much a deadline for economic progress as it is a diplomatic ultimatum," Easley said. "This is why Pyongyang is increasing pressure on Seoul and Washington in the form of announcing plans to bulldoze even stalled inter-Korean projects, such as at Mount Kumgang, while continuing provocative missile tests."