BEIJING, July 11 (Xinhua) - General Secretary of the Communist Party of China Central Committee Xi Jinping, also Chinese president and chairman of the Central Military Commission, exchanged congratulatory messages on Sunday with Kim Jong Un, general secretary of the Workers' Party of Korea, also chairman of the State Affairs Commission and commander-in-chief of the armed forces of the Democratic People's Republic of Korea (DPRK) on the 60th anniversary of the signing of the China-DPRK Treaty of Friendship, Cooperation and Mutual Assistance .