South and North Korea kicked off this year's joint excavation of a medieval royal palace site in the communist North Thursday despite lingering inter-Korean tensions, Seoul officials said.

A ceremony to mark the start of the six-month project was held at the scene in the North's border town of Kaesong, attended by relevant officials and historians from both sides, they said.

Kaesong served as the capital for most of the Goryeo Dynasty (918-1392) and is now home to an industrial complex run by both Koreas.

The two Koreas have conducted six rounds of joint excavations of the site of Manwoldae, a Goryeo Dynasty palace, since 2007. But the progress of the project has been intermittent amid drawn-out tensions between the two Koreas.

This year's excavation will run for six months until Nov. 30, the longest-ever period since the project began.

Manwoldae is part of a group of "historic monuments and sites in Kaesong" that was inducted into the UNESCO world heritage list in 2013. The Manwoldae palace was constructed in 919 but was completely destroyed during the Red Turbans invasions of Korea during the 14th century. (Yonhap)