Sunday's arrival in Singapore of North Korean leader Kim Jong Un, a closely watched figure across the globe, prompted local police to go on full alert ahead of the upcoming historic summit with U.S. President Donald Trump in the city-state.

Kim's plane touched down around 2:30 p.m. A convoy of over 20 vehicles was soon after seen leaving Changi airport, with the leader riding in one of them. From the airport to the St. Regis Hotel where Kim is staying, 12 police motorcycles led the North Korean motorcade.

At a restaurant in the luxury hotel in central Singapore, hotel staff prevented guests from snapping photos of Kim with their smartphones.

"I have been excited since I knew that he would come. I have doubted whether he would really come, but he came," a Japanese women in her 50s, who lives in Singapore, told Kyodo News.

Kim is scheduled to meet with Trump on Tuesday for the first-ever summit between sitting leaders of the United States and North Korea, with the focus on whether Washington and Pyongyang will alleviate security tensions and eliminate the threat of war.

North Korean leader's trip to Singapore is believed to be the longest he has made, and only his second overseas trip by air, since taking office in 2011.

When Kim visited Beijing in March in his first foreign trip as leader, he traveled on a special armored train, following the tradition set by his father and grandfather, former leaders Kim Jong Il and Kim Il Sung.

Early last month, however, Kim visited the northeastern Chinese city of Dalian using his private jet previously used for travel within North Korea. It marked his first international trip by air since succeeding his father as leader, sparking speculation that he would use the same aircraft to visit Singapore.

But at Changi airport on Sunday, Kim descended from an Air China 747, the same one used by high-ranking Chinese officials including President Xi Jinping, Kyodo News confirmed.

As his private jet is a Cold War-era Ilyushin-62, safety concerns may have prompted Kim to make the trip on a more modern aircraft, some analysts say.

South Korea's Yonhap News Agency said that Kim's private jet left Pyongyang for Singapore on Sunday morning, but Kyodo News has not confirmed that the plane landed at Changi airport.