North Korea on Wednesday fired 130 artillery shells into the waters of Yellow Sea near the western sea border it shares with South Korea, although none of the shells landed in the South. The move comes amid rising tensions between the two Koreas over the Northern Limit Line (NLL), a western maritime border, which has been patrolled by the South since the end of the Korean War in 1953. The NLL is, however, not recognized by North Korea, which demands that the line should be drawn much farther south.

The South Korean military called for an emergency meeting following Wednesday’s round of drills and upgraded its military’s response position, but no clashes were reported. Its military was reportedly notified on Wednesday about the drill before its start.

Similar drills in the region have been conducted occasionally by Pyongyang and some of its shells have fallen in the South Korean territory before. In such cases, Seoul responds by firing its own artillery shells, the New York Times reported.

"North Korea's latest maritime firing is a clear act of tension escalation on the northern side of the NLL and our military is standing in all-out military reaction position with a keen eye upon the movement of the North Korean military," the South Korean Joint Chiefs of Staff said, according to Yonhap.

Earlier this month, North Korea threatened to launch "unannounced targeted strikes” against the South’s navy, after two South Korean navy speedboats allegedly made a “military provocation” by encroaching into North’s waters at the Yellow Sea. However, South Korea has denied the accusations.

In 2010, North Korea had allegedly torpedoed a ship belonging to the South Korean navy in the disputed waters and also attacked one of the South’s islands with artillery. In the two attacks, 50 South Korean nationals were reportedly killed.

Last October, the two sides exchanged warning shots after a North Korean patrol boat violated the NLL border. Later that month, firing was reported along the Korean border after the North shot down some balloons carrying anti-Pyongyang propaganda leaflets and a few of its shots landed in South Korea. At the time, North Korea threatened the South that the latter would face "uncontrollable catastrophe" if activists continued the leaflet campaign.