Kim Jong Un on Friday became the first North Korean leader to cross the border with the South after the Korean War, the latest in a series of remarkable developments emerging from his sudden embrace of diplomacy since the beginning of this year.

During his meeting with South Korean President Moon Jae In, Kim at times wore a pained expression on his face, but for the most part communicated with the South's president with grand gestures.

Clad in a black Mao-style suit, a smiling Kim, who is in his 30s, shook hands with the 65-year-old Moon as the two men stood on their respective sides of the demarcation line running through the border village of Panmunjeom in the Demilitarized Zone.

(Korea Summit Press Pool)

After Kim stepped over the line with a smile, they both briefly stepped into the North's territory before returning to the South Korean side hand in hand in a show of unity.

Journalists watching the scene on a giant screen erupted in cheers at a media center set up at the Korea International Exhibition Center, or KINTEX, 30 kilometers away from the venue of the leaders' meeting.

The two leaders received bouquets of flowers from a boy and a girl and then walked together on a red carpet behind a military band clad in traditional costumes. A South Korean honor guard welcomed Kim.

Kim repeatedly expressed hopes for peace between the two Koreas, which remain technically at war since the 1950-1953 Korean War ended in a cease-fire.

"A new era will come from now on," Kim wrote before the summit in a signature book at the Peace House, a South Korea-controlled building at the truce village, according to the Inter-Korean Summit Press Corps.

At the outset of the summit, which was open to the media, Kim told Moon, "I hope to write a new chapter between us, so this is a starting point for us."

(Korea Summit Press Pool)

Later Friday, cold noodles from the famous Okryu-gwan restaurant in Pyongyang will be served when the two leaders dine together.

"We managed to bring cold noodles from Pyongyang. I hope that the president will eat the cold noodles comfortably," Kim told Moon with a smile.

While talking with Moon about an idea of realizing a high-speed train connecting the two Koreas, Kim was quoted by a South Korean official as saying he was concerned that his country may inconvenience the South as the North's transport infrastructure is not as developed.

Kim had been seen as a ruthless and impulsive leader as he reportedly executed close aides and was engaged in a fiery verbal tit-for-tat with U.S. President Donald Trump last year over North Korea's development of nuclear weapons and long-range missiles.

But he has recently appeared in the media more frequently, often in settings that purportedly showcased his statesmanlike qualities, giving the impression to many, including those who were skeptical about his abilities, that he may actually be rational and astute.

After months of sabre-rattling and missile and nuclear tests that raised tensions on the Korean Peninsula, Kim suddenly extended an olive branch, saying in his New Year's address on Jan. 1 that he would prepare for his country's participation in the Feb. 9-25 Pyeongchang Winter Olympics hosted by South Korea.

Kim subsequently invited Moon to visit Pyongyang via his sister and close aide, Kim Yo Jong, who had previously travelled to the South in February for the Olympics.

Less than a month later, in early March, Kim held talks with Moon's special envoys in Pyongyang. It was his first direct contact with South Korean officials since he became North Korea's leader following the death of his father Kim Jong Il in December 2011.

(Korea Summit Press Pool)

That meeting took place "in a compatriotic and sincere atmosphere," with Kim telling a joke that he would not wake up Moon anymore by test-firing ballistic missiles in the early morning, a South Korean government source said.

South Korean culture minister Do Jong Whan, who visited Pyongyang earlier this month as the head of a musical troupe and met with Kim, says the leader has a "vibrant" character and a "humorous" side.

In late March, Kim made his first foreign trip since assuming power and held a surprise summit with Chinese President Xi Jinping in Beijing.

Since the trip, official media have begun reporting his public appearances more frequently, such as at the performance staged by the South Korean musical troupe and another one by a visiting Chinese art troupe.

Kim made Time magazine's list of the world's 100 Most Influential People of 2018 released earlier this month.

Read more on inter-Korean summit:

Koreas confirm goals of "complete" denuclearization, ending war

Kim Jong Un voices hope for start of new chapter of Korea's history

Moon, Kim shake hands, raising hope for formal end of Korean War

South Korea's Moon no stranger to inter-Korean diplomacy

North Korea's Kim remains an enigma on world stage

Inter-Korea summit media center booming, some feel let down