(Photo: CGTN)

The Republic of Korea (ROK) expressed regret Monday over the Democratic People's Republic of Korea (DPRK)'s artillery firing drills in an inter-Korean border island. 

Defense ministry spokesperson Choi Hyun-soo told a press briefing that the artillery firing drills were in violation of the comprehensive military agreement, which the military authorities of the two Koreas agreed to and had been fully implemented. 

Choi urged the DPRK to immediately stop all military acts that are feared to escalate military tension in inter-Korean border areas, and to fully comply with the military agreement to prevent the recurrence of such drills. 

The comment came after DPRK's official Korean Central News Agency (KCNA) reported earlier in the day that DPRK leader Kim Jong Un inspected a military unit on Changrin Island that conducted the live-fire artillery drills. 

The Changrin Island is located just north of the inter-Korean maritime border. 

The coastal artillery company's actions during Kim's visit to the western coast's Changrin Islet "fully showed their gun firing skills" and "delighted the supreme leader", according to the KCNA. It didn't say when the visit took place, and it wasn't clear what specific weapons were fired. 

It was in violation of the military agreement, which was signed by defense chiefs of the two Koreas during the third summit between Kim and ROK President Moon Jae-in in Pyongyang last September. 

Under the agreement, the ROK and the DPRK agreed to stop all hostile acts in border areas, setting up ground, maritime and air buffer zones to prevent accidental clashes. 

Meanwhile, Kim also visited the women's company under Unit 5492 of the Korean People's Army stationed on the country's southwestern coast.  

Relations between the two Koreas improved greatly last year as Kim engaged in talks with the US over the fate of his advancing nuclear arsenal. Kim met US President Donald Trump in Singapore in June last year in what was the first such DPRK-US summit since the end of the 1950-53 Korean War. Kim also met Moon three times last year.