A senior Chinese official is in North Korea to mark the 50th anniversary of the friendship treaty between the two countries.

Chinese Vice Premier Zhang Dejiang is leading a delegation that is stressing the relationship between Beijing and Pyongyang. He met Tuesday with Kim Yong Nam, the head of North Korea's Supreme People's Assembly.

North Korean state media showed video of the delegates visiting a university and other sites in the North Korean capital.

The delegation arrived Sunday and leaves Wednesday.

China is North Korea's strongest ally and a main source of its energy and food imports. China also has been the host of six-nation talks aimed at ending North Korea's nuclear weapons programs. The talks have been stalled for more than two years.