China's special envoy to North Korea has paid his respects at the mausoleum of former North Korean leaders in Pyongyang, North Korea's state-run news agency said Monday.

Song Tao, the head of the International Liaison Department of the Communist Party of China, has been visiting North Korea since Friday. Chinese President Xi Jinping sent Tao as his special envoy to inform Pyongyang of the outcome of the party's recent congress.

"Comrade General Secretary of the Communist Party of China Xi Jinping's special envoy, Comrade Song Tao, and his delegation have paid respects at Kumsusan Palace of the Sun" on Sunday, the Korean Central News Agency reported.

Song toured the mausoleum's exhibition rooms containing medals and vehicles used by former leaders Kim Il-sung and Kim Jong-il and left a message in a guest book there that reads, "I express heartfelt longing for Comrade Kim Il-sung and Kim Jong-il who were great leaders of the Korean people and friendly mates of China," according to the KCNA report.

Also on Sunday, the special envoy, accompanied by the Chinese ambassador to North Korea, laid flowers at a tower in Pyongyang that symbolizes North Korea-China friendship, according to the report.

Song also traveled to Hoechang County, west of Pyongyang, to tour what was Chinese military forces' headquarters during the 1950-53 Korean War, it also said.

The report did not say whether Song had met with sitting North Korean leader Kim Jong-un. Song's North Korean trip is being closely watched by the outside world for any signs of a possible breakthrough in the long-stalled North Korean nuclear issue.

On Friday, Song met with Choe Ryong-hae, a high-ranking North Korean official, and had talks with Ri Su-yong, vice chairman of the Central Committee of the North's ruling Workers' Party, the next day. They exchanged views about the situation on the Korean Peninsula and in the region and on bilateral relations, the KCNA said.

 South Korea's unification ministry later said whether the Chinese envoy has met with Kim Jong-un was unknown as of Monday morning.

"Whether special envoy Song talked with Kim Jong-un or delivered President Xi's handwritten letter (to Kim) has not be reported or confirmed yet, and (the ministry) will continue to follow the development closely," ministry spokesman Baik Tae-hyun said in a press briefing.

Experts predicted Song may wrap up his trip and return to China on Monday when China's flag carrier, Air China, flies one of its two weekly flights linking Beijing and Pyongyang. The other flight is on Friday. (Yonhap)