North Korea’s senior official Ri Su Yong arrived in Beijing Tuesday, South Korea's Yonhap News Agency reported. This is the first visit by any top North Korean official to China since the reclusive nation conducted a series of nuclear tests and missile launches defying sanctions by world powers.

Ri, who serves as a career diplomat and is also the newly promoted vice chairman for international affairs of the ruling Workers' Party, reached Beijing with a large entourage of officials after leaving North Korea's capital city, Pyongyang, by plane, local sources told Yonhap. The details of Ri’s visit were not immediately available. Relations between China and North Korea had strained after the latter carried out nuclear tests and missile launches, the report said.

Ri acted as North Korea's foreign minister until he was named a member of the politburo during the recent congress of the ruling Workers’ Party.

Beijing is widely seen as the reclusive nation’s diplomatic and economic protector. Although China criticized Pyongyang’s recent nuclear test, experts say Beijing may not go too far against its old ally. China may be reportedly concerned about an influx of refugees from North Korea across its own border and to South Korea if the Kim Jong Un-led government was toppled.

In a separate development, a missile launched by North Korea from its east coast early Tuesday appeared to have failed, South Korea’s Joint Chiefs of Staff (JCS) said. Sources told Yonhap that the missile was likely a Musudan intermediate-range ballistic missile. Pyongyang had launched three Musudan missiles in April, all of which reportedly ended in failure.

“North Korea attempted to launch an unidentified missile from the region near Wonsan at around 5:20 a.m., but it is presumed to have been unsuccessful,” the JCS reportedly said.

The sanctions-hit country has conducted a series of missile and nuclear tests since the beginning of this year and its leader has called to strengthen the country’s defense capabilities. Pyongyang has also claimed to have secured intercontinental ballistic missile technologies like reentry and engine technologies.