SEOUL, South Korea (AP) — South Korea's navy on Friday fired warning shots to chase away two North Korean ships after they briefly crossed a disputed western sea boundary, Seoul defense officials said. The North Korean ships — one military vessel and the other a fishing boat — were in South Korean-controlled waters for less than 10 minutes Friday morning before they retreated, the officials said requesting anonymity citing department rules. In February, South Korea also fired several rounds of warning shots as a North Korean patrol boat moved south of the boundary but no clash occurred either.