A North Korean patrol vessel is seen in the distance behind a Chinese fishing boat. South Korea's military seized a North Korean fishing boat that crossed the maritime border between the two Koreas, March 8. Korea Times file

A North Korean patrol boat retreated Tuesday after crossing the western maritime border into South Korean waters to chase a purportedly stray boat, according to military officials here.

The patrol boat crossed the Northern Limit Line (NLL), the de facto inter-Korean maritime border, at 9:49 a.m. as it tracked the other ship that breached the NLL 15 minutes earlier, the Joint Chiefs of Staff (JCS) said.

The South Korean Navy drove the patrol boat back to the North with warning shots and messages, and seized the other ship carrying seven crewmembers, including six wearing military uniforms.

The South has sent messages to the North about the border crossing incident twice thorough commercial and military communication lines, the JCS said.

The seven unarmed North Koreans are said to have no intention of defecting to the South and claim their ship accidentally veered into South Korean waters.

The incident came just a day ahead of South Korea's presidential election and amid renewed tensions over recent North Korean missile launches, including a purported "reconnaissance satellite" development test Saturday. (Yonhap)