The South Korean news agency Yonhap reported on December 9, 2015, that the South Korean Navy fired warning shots at a Chinese patrol boat that crossed the Yellow Sea border between Seoul and Pyongyang and sailed 2 kms into South Korean waters. South Korea's Navy fired after broadcasting six warnings through radio communications. The Chinese Navy vessel had been monitoring Chinese ships poaching fish across the Yellow Sea border. The South Korean side mistook the Chinese boat for a North Korean patrol, which regularly violate the sea border known as the Northern Limit Line (NLL).