North Korea's deputy prime minister has admitted economic difficulties and called for South Korea's assistance, a South Korean presidential official said Friday, in a rare appeal by the North to try to boost its economy.

Ri Ryong-nam made the comments in a meeting with top South Korean business executives earlier this week, Kim Hyun-chul, a special economic adviser to South Korean President Moon Jae-in, told reporters of the meeting.

The executives, including Samsung Electronics Vice Chairman Lee Jae-yong, accompanied Moon on his first trip to Pyongyang for the summit with North Korean leader Kim Jong-un earlier this week.

The high-profile visits by Lee and other top executives indicated that North Korea, one of the world's poorest countries, wants to attract South Korean investment and technology to improve its economy.

North Korea's gross domestic product, calculated as power purchasing parity, is estimated at US$40 billion in 2015, according to the CIA Factbook, a fifth of the 2017 annual sales of Samsung Electronics, which reached $213 billion.

The economic adviser also said Ri had conversations with Hyundai Group chairwoman Hyun Jeong-eun and Park Yong-maan, chairman of the Korea Chamber of Commerce and Industry, a major South Korean business lobby. No details of those conversations were disclosed.

Hyundai Asan, the inter-Korean business arm of Hyundai Group, was a key partner in a joint factory park in North Korea's border city of Kaesong as well as a joint tour program at Mount Kumgang, a scenic mountain resort on the North's east coast.

The two projects -- prominent symbols of reconciliation between the two separated countries -- have been suspended for years due to tensions. (Yonhap)