The powerful uncle of North Korean leader Kim Jong-un returned home Saturday after a six-day visit to China that included Beijing's agreement to help develop special economic zones in the impoverished nation and meetings with China's president and premier, the two countries' media said.

The North's Korean Central News Agency said Jang Song-thaek, the chief of the central administrative department of the Workers' Party, boarded a Koryo Air flight that departed Beijing's Capital Airport at 1:30 p.m.

The trip by Jang, who also serves as vice chairman of the North's National Defense Commission, was seen as aimed at winning economic cooperation from the North's most important ally to help revive the North's moribund economy.

A day before the trip back home, Jang met with Chinese President Hu Jintao and Premier Wen Jiabao who both praised him for making "huge amount of work for the friendly relations between China and North Korea."

Earlier this week, the two countries agreed to accelerate efforts to jointly develop the Rason, Hwanggumphyong and Wihwado economic zones in North Korea, the most tangible outcome of Jang's trip. His delegation of some 50 officials included key economic technocrats.

Jang is the highest-ranking North Korean official to visit China since Kim Jong-un took over as the North's leader after his father Kim Jong-il died in December. Jang is the husband of the late leader's younger sister, Kim Kyong-hui.

Media have speculated his trip may be a sign the North's leader could visit China.

Jang also toured Chinese provinces near the border with the North, such as Jilin and Liaoning.

(Yonhap News)