North Korea fired three ballistic missiles off its east coast Monday, South Korea’s military said, in a new show of force that comes as the leaders of the Group of 20 major economies held a summit in China, the North’s main diplomatic ally.

The missiles were fired into the Sea of Japan (East Sea) from the North’s Hwangju county at around 0300 GMT, a defense ministry spokesman said, more sabre-rattling that follows a submarine-launched ballistic missile test some two weeks ago.

“They are speculated to be Rodong missiles with a range of 1,000 kilometers and were fired without navigational warning to Japan,” the spokesman said in a statement.

“North Korea’s ballistic missile launch is a direct violation of U.N. Security Council resolutions aimed at showing off its nuclear and missile capabilities during the G20 summit,” he added.

Monday’s missile launch came hours after South Korean President Park Geun-Hye and Chinese President Xi Jinping met on the sideline of the G20 Summit in Hangzhou.

Park told the Chinese President that the North’s fourth nuclear test and its ballistic missile launches this year threatened regional peace and posed a challenge to South Korea’s ties with China, Yonhap news agency reported earlier.

During the meeting, Xi reaffirmed China’s commitment to realizing the denuclearization of the Korean peninsula, China’s state news agency Xinhua reported on Monday.

Xi also told Park that Beijing opposed the proposed deployment of a THAAD anti-missile system in South Korea, which Seoul and the United States have said is designed to counter an increasing missile threat from North Korea.

China is the North’s sole major ally and economic lifeline but ties have been strained recently over the Pyongyang’s nuclear and missile tests that raised tension on the peninsula.

North Korea has staged a string of missile tests this year, with the most recent August 24 submarine-launched ballistic missile flying 500 kilometers towards Japan — a range that far exceeded that of the North’s previous sub-launched missile tests.

North Korean leader Kim Jong-Un described the August test as the “greatest success” and said it put the U.S. mainland within striking range.

The launch was widely-condemned by the U.S. and other major powers, but did mark what weapons analysts said was a clear step forward for North Korea’s nuclear strike ambitions.

A proven submarine-launched ballistic missile system would allow deployment far beyond the Korean peninsula and a “second-strike” capability in the event of an attack on the North’s military bases.