SEOUL-- China's special envoy to Pyongyang returned to Beijing on Monday, ending his four-day visit, while it was immediately unknown whether he met with North Korean leader Kim Jong-un.

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

China's Xinhua News Agency reported that the envoy exchanged "views on the Korean Peninsula issue" with North Korean officials during the visit.

North Korean ambassador in China Ji Jae-ryong was seen greeting the envoy's return at Beijing Capital International Airport.

It was not immediately confirmed whether Song had met with sitting North Korean leader Kim Jong-un. Song's North Korean trip was 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 Korean Central News Agency (KCNA) said.

The North Korean state-run news agency said Monday that Song has paid his respects at the mausoleum of former North Korean leaders in Pyongyang.

"Comrade General Secretary of the Communist Party of China Xi Jinping's special envoy, Comrade Song Tao, and his delegation have paid their respects at Kumsusan Palace of the Sun" on Sunday, the KCNA 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 read, "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 the 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.

South Korea's unification ministry said whether the Chinese envoy 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.

The KCNA also made a brief report on Song's return to Beijing on Monday, but did not provide further details.

Source: Yonhap News Agency