Japanese Foreign Minister Toshimitsu Motegi laid claim to South Korea's Dokdo islets while addressing the opening of the Diet's regular session on Monday.

It's the eighth straight year since 2014 that Tokyo's top diplomat has made the territorial claim during the annual speech outlining the direction in diplomatic policies.

Motegi said that Takeshima, the Japanese name for Dokdo, belongs to Japan historically and under international law and vowed to respond cool-headedly based on this stance. 

He also assessed that relations with South Korea are in a grave state due to the wartime issues of forced labor and sex slavery.

The foreign minister then blasted a recent South Korean court ruling that ordered Tokyo to compensate sex slavery victims as ​"very regrettable" and a "totally unthinkable" situation in terms of international law and bilateral ties. 

He added that during phone talks with Seoul's Foreign Minister Kang Kyung-wha, he requested the Korean government take swift action to correct its violations of international law.

Alongside the criticism, Motegi called South Korea an important neighbor and stressed that cooperation with Seoul and Washington is critical to regional stability and responding to North Korea.