SEOUL/BEIJING -- North Korean leader Kim Jong-un on Tuesday began a two-day visit in China that may include a summit with President Xi Jinping, according to sources.

Kim's third visit to China in three months follows his summit meeting with US President Donald Trump in Singapore on June 12 in which Kim affirmed his commitment to complete denuclearization in return for security guarantees and a new relationship with the US.

After an Air Koryo flight carrying Kim arrived at Beijing's Capital International Airport in the morning, Kim immediately headed to the Diaoyutai state guest house in Beijing, the first destination of Kim's two-day trip in China, the sources said.

Armed police cruisers guarded Beijing's Tiananmen area as two VIP sedans, appearing to be carrying Kim, passed through the area and entered the state hotel for top-level guests.

The sedans were followed by a convoy of vehicles, including some 10 high-end passenger vehicles, 10 buses and an ambulance.

His trip to China is the third this year, following the ones in March and May when he met Chinese President Xi Jinping.

Chinese media confirmed Kim's visit to Beijing. China's state-run CCTV said Kim will stay in China from Tuesday to Wednesday. It did not provide more details.

Japan's Nikkei newspaper earlier said that Kim may travel to Beijing by plane as early as Tuesday. It added that relevant security measures were seen being made in the Chinese capital.

Signs were detected that high-ranking officials from North Korea arrived in Beijing.

Aviation sources said that Air Koryo's An-148 airplane were spotted taking off in Pyongyang early in the day and landing at Beijing's Capital International Airport at about 9:30 a.m. It has not been confirmed whether the North Korean leader was on board.

A separate North Korean freight plane also landed at the airport at about 8:40 a.m. It is said to be the same plane used to carry luggage and other necessary equipment for Kim's trip to Singapore for his summit with Trump last week.

A group of vehicles including luxury sedans and buses were seen departing from the airport.

Security has been tightened around the Diaoyutai State Guesthouse, with additional police officers deployed, spawning speculation that a high-ranking foreign official's visit might be imminent.

Neither China nor North Korea has officially confirmed Kim's trip to China yet.

The Nikkei said that Kim would use the trip to share the details of the summit and discuss bilateral cooperation with China going forward.

Observers generally agree that Kim's visit to China this time is apparently intended to brief Xi on the outcome of his summit with Trump but added that he could enlist support from China ahead of talks on how fast it will have to give up its nuclear weapons program.

For China, it could be intended to strengthen its voice in the fast-paced nuclear diplomacy mostly being led by the US and South Korea, they said.

"It appears that Kim intends to express his gratitude to China for providing support during his summit with Trump, such as offering a plane, while explaining the major agenda items discussed during the summit and pushing to take the initiative through consultation for the future situation," Shin Beom-chul, a senior fellow at the Asan Institute for Policy Studies, said.

Yoo Hyun-jung, a senior researcher at the Institute for National Security Strategy, said that Kim's third visit to Beijing in about three months must be meant to enlist support from China, especially in easing sanctions imposed on Pyongyang now that tensions are easing.

The US has said that there will be no sanctions relief until Pyongyang's denuclearization. The North has claimed that Trump expressed his intention during the summit to lift sanctions "along with advance in improving the mutual relationship through dialogue and negotiation." (Yonhap)