North Korean leader Kim Jong Un has agreed to hold a landmark summit with South Korea's president and impose a moratorium on nuclear and missile tests if his country holds talks with the US, a senior Seoul official said.

Chung Eui-yong, South Korea's presidential national security director, said the two Koreas agreed to hold their third-ever summit at a tense border village in late April.

He also said the leaders will establish a "hotline" communication channel to lower military tensions, and would speak together before the planned summit.

Mr Chung led a 10-member South Korean delegation that met Mr Kim during a two-day visit to Pyongyang, North Korea's capital. They returned on Tuesday.

The agreements follow a flurry of co-operative steps taken by the Koreas during last month's Pyeongchang Olympics in South Korea.

Tensions had run high during the previous year because of a barrage of North Korean weapons tests.

North Korean leader Kim Jong Un, left, shakes hands with South Korean National Security Director Chung Eui-yong in Pyongyang, North Korea.

The two past summits, in 2000 and 2007, were held between Mr Kim's late father, Kim Jong Il, and two liberal South Korean presidents.

They resulted in a series of co-operative projects between the Koreas that were scuttled during subsequent conservative administrations in South Korea.

Mr Chung said North Korea had agreed to suspend nuclear and missile tests for as long as it holds talks with the US.

Pyongyang also made it clear it would not need to keep its nuclear weapons if military threats against it are removed and it receives a credible security guarantee, Mr Chung said.