It said Meng Jianzhu, Chinese state councillor and public security minister, "warmly congratulated" Kim Jong-Il on his re-election in September as ruling communist party general secretary and his son Kim Jong-Un upon his election as vice-chairman of the party's Central Military Commission.
Meng hailed "the successful solution of the issue of succession to the Korean revolution"; the news agency said in an unusual direct reference to the succession issue.
The Chinese minister met leader Kim Monday to pass on "kind greetings" from President Hu Jintao and other officials, the agency said.
He is in Pyongyang at the start of a tour that will also take him to Laos, Singapore and Malaysia.
Meng "warmly congratulated" Kim Jong-Il on his birthday this Wednesday and presented gifts to the leader and to Jong-Un,the agency said.
China is the North's sole major ally and its economic prop.
Kim Jong-Il travelled there twice last year in what was seen partially as an attempt to secure support for Jong-Un, believed aged 27, as eventual successor.
The son was in September made a four-star general and appointed vice chairman of the Central Military Commission, which oversees the 1.2 million-strong armed forces headed by his father.