South Korea's military today fired warning shots today to repel a North Korean merchant ship after it violated their disputed western sea boundary.<br />'' <br />'' Seoul's Joint Chiefs of Staff said that it believes the North Korean ship crossed the sea boundary due to bad weather and engine problem. No further violence was reported.<br />'' <br />'' It's the second time that South Korea has fired warning shots to drive back a North Korean ship in the area since South Korea's current liberal government took office in 2017.<br />'' <br />'' The first incident happened in September.<br />'' <br />'' Ties between the two Koreas are strained amid a stalemate in US-led diplomacy on ending the North Korean nuclear crisis.<br />''