Historic sites in North Korea's ancient city of Gaeseong were added to the world heritage list of UNESCO on Sunday, official sources said.

The decision was made during the 37th session of UNESCO's World Heritage Committee in Phnom Penh, Cambodia, earlier in the day, sources following the event said. The session is set to continue until Thursday.

The decision has been widely expected as the sites were recommended last month by the Paris-based International Council on Monuments and Sites, an advisory panel conducting on-site surveys of nominations for UNESCO.

Gaeseong was the capital of the Goryeo Dynasty that ruled the Korean Peninsula from 918 until 1392 when it was replaced by the Joseon Dynasty. It now sits just outside the inter-Korean border that separates the two Koreas roughly along the 38th parallel.

Pyongyang requested Gaeseong's historic monuments be registered as a global heritage in mid-2012.

In 2004, North Korea successfully added tombs from the Koguryo Kingdom (37 B.C.- A.D. 668) to the world heritage list. The powerful kingdom once ruled most of what is now North Korea and northeastern China.

The group of historic monuments and sites in Gaeseong is the second world heritage listing for the North and the 12th on the Korean Peninsula.

The monuments and sites are located within the built-up area of Gaeseong and extend into the foothills of the mountains to the west of the town.

They comprise 12 separate property components, including five separate sections of the Gaeseong city walls. The other seven are: the Manwoldae Palace archaeological site and remains of the Gaeseong Chomsongdae, an astronomical and meteorological observatory; the Gaeseong Namdaemun gate, the main southern city gate; Goryeo Songgyungwan, a former high state education institute where Goryeo national officials were educated; Sungyang Sowon, a Confucian private school; Sonjuk Bridge and Phyochung Monuments, the latter being two commemorative steles; the Mausoleum of King Wang Geon, the founder of the Goryeo Dynasty, with seven associated tomb clusters and the Myongrung tomb cluster; and the Mausoleum of King Gongmin, the 318th king of Goryeo.

The monuments and sites "exhibit the synthesis of cultural, spiritual and political values of pre-existing states unified under the Goryeo and the interchange of such values with other neighboring states," the ICOMOS report said.

The report also called them "an outstanding example of a capital city in transition from Buddhism to neo-Confucianism as a guiding philosophy for government."

"(The decision) is the pride of the Korean race and the humanity," an unidentified official from North Korea said during the event in a thank-you message.

"A new guideline on preserving the historical sites in Gaeseong is set to be enforced soon, and the central government has also revised rules on protecting cultural assets," the official said.

"(The decision) has given a legal ground to enhance the protective measures on the cultural heritage of Koreans and the world."

"The Democratic People's Republic of Korea will continue to fulfill its mission and duty to abide by UNESCO's convention on the protection of world cultural heritage," the official added. (Yonhap News)