The Democratic People's Republic of Korea (DPRK) fired artillery shells Thursday into waters off the west coast of the Korean peninsula, for the third such move in two days, South Korea's Joint Chiefs of Staff (JCS) said.

"South Korean military based in Yeonpyeong island heard shootings around 8:10 a.m. (2310 GMT), but we are not sure where the shells landed," a JCS official told Xinhua.

Seoul's Yonhap News Agency reported earlier Thursday the DPRK fired several artillery shells at 8:05 a.m. (2305 GMT) and again at 8:15 a.m. (2315 GMT) into waters near the contentious sea border called Northern Limit Line (NLL) off the west coast of the Korean peninsula.

Thursday's move is defiant of South Korean military's warning a day ago to stop "provocative" acts and cancel DPRK's designation of no-sail zones which includes South Korean waters, according to local media.

On Wednesday, the DPRK fired scores of artillery shells around 9:05 a.m. (0005 GMT) and 3:25 p.m. (0625 GMT), respectively, into waters near the contentious sea border called Northern Limit Line (NLL) off the west coast of the Korean peninsula, within the range of no-sail zones recently designated by the DPRK.

South Korea responded to the first round of firing on Wednesday by firing some 100 Vulcan cannons as warning shots, but only sent two warning messages without firing warning shots in response to the later shootings in what local media said was an effort to prevent an unnecessary escalation of tension.

There were no casualties or injuries reported as the two sides fired into the air and not at each other.

The contentious maritime border, where the latest naval skirmish between the two Koreas took place in November last year, was fixed unilaterally by the U.S.-led United Nations Command after the 1950-1953 Korean War.