North Korea has designated another two firing zones near its disputed Yellow Sea border with South Korea. The two new maritime firing zones would be effective for four days from Friday. South Korean officials today said the move will raise the prospect of more artillery fire. <br/><br/>A Joint Chiefs of Staff spokesman said South's military is closely watching for possible artillery fire off Baengnyeong and Daecheong islands near the Northern Limit Line sea border. After declaring two no sail zones, North Korea last week fired 370 shells into the sea near the border over three days, heightening tensions on the Korean peninsula.<br/><br/>The North said it was staging a routine exercise but South Korea and the United States described the firing as provocative. The Yellow Sea border was the scene of deadly naval battles in 1999 and 2002 and of a firefight last November which left a North Korean patrol boat in flames.