South Korea's military is on high alert on Saturday after North Korea declared no-go zones near its disputed sea border with the South sparking fears that the North could begin firing weapons. <br/><br/>A Joint Chiefs of Staff spokesman said the military has deployed anti-artillery fire finder radar systems in Baengnyeong Island and Yeonpyeong islands on Friday evening. <br/><br/>According to Yonap news agency, the South had also stepped up air and naval surveillance along the inter-Korean border. South Korea's Joint Chiefs of Staff said the North has declared a total of eight no-sail zones, four in the Yellow Sea and four others in the Sea of Japan, off its northeast coast on Friday evening and they will be effective for three days from Saturday. <br/><br/>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.