North Korean leader Kim Jong Un's sister met South Korean officials on their heavily defended border on Wednesday to deliver flowers and her brother's condolences over the death of a former South Korean first lady.

The sister, Kim Yo Jong, visited the border village of Panmunjom in the demilitarised zone separating the two Koreas to pay her respects to Lee Hee-ho, the widow of former South Korean President Kim Dae-jung, a South Korean official said.

Lee died in the South Korean capital, Seoul, on Monday.

Kim Dae-jung tried to promote better ties on the divided Korean peninsula and became the first South Korean leader to meet North Korea's then-leader, Kim Jong Il, in 2000.

South Korean officials said Kim Yo Jong, who has emerged over the past 18 months as a top aide to her brother, did not have any particular message or letter for South Korean President Moon Jae-in. The two sides talked for about 15 minutes.

"She said she hopes the South and the North will continue cooperation, upholding Ms Lee Hee-ho's resolve for reconciliation and cooperation between the people," South Korea's national security adviser, Chung Eui-yong, told reporters.

"Today, she focused on cherishing the deceased and sharing condolences."

Moon's press secretary told a separate briefing that Kim Yo Jong also said her brother had a "special feeling" towards Lee.

Kim Yo Jong's visit came exactly a year after her brother and U.S. President Donald Trump agreed at the first U.S.-North Korea summit in Singapore to work towards the denuclearisation of the Korean peninsula, easing fears of war.

Those talks have since stalled and inter-Korean engagement has dwindled.

Kim Dae-jung, president from 1998 to 2003, is known for championing a so-called Sunshine policy of engagement with North Korea. Last year's detente between the two Koreas was seen as a revival of that policy.

Reclusive North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.

Last year saw a number of high-level meetings between South and North, including three summits between Kim Jong Un and South Korea's President Moon.

Kim Yo Jong visited South Korea for the Winter Olympics in February 2018 and also accompanied her brother at the summits.