Kim Jong-un has become the first North Korean leader to cross into the South since the signing of the Korean War armistice in 1953, attending an historic summit with his southern counterpart Moon Jae-in.

Key points: Mr Moon also crossed briefly across demarcation line into the North

Mr Moon also crossed briefly across demarcation line into the North Mr Kim wrote "A new history starts now" in Peace House guest book

Mr Kim wrote "A new history starts now" in Peace House guest book Leaders expected have planted a memorial tree at border truce village

South Korean President Mr Moon personally greeted Mr Kim with a handshake on the demarcation line in the border truce village of Panmunjom, in the demilitarised zone (DMZ) between the countries.

The leaders posed for a photo together before crossing the demarcation line hand in hand, kicking off the first leadership summit between the divided countries in more than a decade.

Mr Kim also invited Mr Moon to step briefly across the demarcation line into North Korea.

The meeting, aimed at ending their decades-long conflict and easing tensions over the North's nuclear weapons program, comes weeks before Mr Kim is due to meet US President Donald Trump.

Mr Kim was accompanied by nine officials, including his sister Kim Yo-jong, who led the North's delegations to the Winter Olympic Games in South Korea earlier this year.

The South's delegation included Mr Moon's ministers for foreign affairs, defence and unification.

The two leaders were handed flowers by a South Korean boy and girl from a village in the demilitarised zone.

Walking on a red carpet rolled out for the two heads of state, the pair were met by a South Korean honour guard in historical costumes and playing traditional music.

Kim Jong-un (left) and Moon Jae-in walk together at the border village of Panmunjom in the demilitarised zone. ( AP: Korea Summit Press Pool )

'A new history starts now'

Mr Kim wore glasses and his trademark black Mao suit, while the rest of the North Korean delegation appeared in military uniforms or Western attire.

Mr Kim and Mr Moon then walked to the Peace House in Panmunjom.

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"A new history starts now. An age of peace, from the starting point of history," Mr Kim wrote in Korean in the book, dating and signing the entry.

During their private meeting, Mr Kim told Mr Moon he came to the summit to end the history of conflict and joked he was sorry for keeping Mr Moon up with his late-night missile tests, a South Korean official said.

Mr Kim told Mr Moon he would be willing to visit the presidential Blue House in Seoul, and wanted to meet "more often" in the future, the official said.

After talks lasting more than an hour-and-a-half behind closed doors, Mr Kim was driven back to the North side just before noon in a black limousine flanked by guards who ran alongside.

Crossing the border, the vehicle had to drive across a lawn, as there is not a road linking the two sides at that spot.

Mr Kim and Mr Moon are expected to jointly announce the outcome of their summit in a few hours.

Six people, including Mr Kim and Mr Moon, were seen at the round table inside the meeting room at the start of the summit. ( AP: Korea Summit Press Pool )

Following lunch, the two leaders planted a memorial tree before resuming their meeting, and are expected to finish the evening with dinner and a film.

The United States is hopeful talks between Mr Kim and Mr Moon will make progress on achieving peace and prosperity, the White House said in a statement as the two men began their summit.

The White House also said it looked forward to continuing discussions with South Korea in preparation for the planned meeting of Mr Trump and Mr Kim in the coming weeks.

Mr Kim and Mr Trump are expected to meet in late May or June, with Mr Trump saying on Thursday he was considering several possible dates and venues.

Just months ago, Mr Trump and Mr Kim were trading threats and insults as North Korea's rapid advances in pursuit of nuclear-armed missiles capable of hitting the United States raised fears of a fresh conflict on the Korean Peninsula.

Sorry, this video has expired South and North Korean leaders plant tree in symbolic act (Image: AP)

Earlier today, North Korea's official KCNA news agency said Mr Kim would "open-heartedly discuss with Mr Moon all the issues arising in improving inter-Korean relations and achieving peace, prosperity and reunification of the Korean Peninsula".

The two countries are technically still at war because the Korean War ended in a truce, not a peace treaty.

Just days before the summit, Mr Kim said North Korea would suspend nuclear and long-range missile tests and dismantle its only known nuclear test site.

Mr Moon travelled to the meeting in a large motorcade, stopping briefly to greet dozens of summit supporters waving South Korean flags near the Blue House.

People hold the Korean unification flag as they watch a news report on the inter-Korean summit. ( Reuters: Kim Hong-ji )

The two neighbours are expected to release a joint statement — possibly called the Panmunjom Declaration — that could address denuclearisation and peace, and an improvement in relations, South Korean officials said earlier.

John Blaxland from the Australian National University said a statement of intent would lay the groundwork for a meeting between Mr Kim and Mr Trump.

"Of course that is a delicate issue, because this gets to the question of legitimacy. Who is the most legitimate ruler of the Korean Peninsula? Is it Kim Jong-un or Moon Jae-in in the South? President Trump has an important role to play," he told ABC News.

"Of course, the other interesting player in this is not just China, but Japan.

"[Prime Minister] Shinzo Abe has engaged with President Trump, keen to make sure he doesn't forget about Japan, because Japan is very worried about what happens on the Korean Peninsula.

"This could significantly affect Japan's security as well."

Kim Jong-un is accompanied by nine officials, including his sister Kim Yo-jong. ( Reuters: Korea Summit Press Pool )

ABC/Reuters