North and South Korea have each held artillery firing drills near their maritime buffer zone on Friday, as tensions ratchet up again on the peninsula. North Korea fired more than 200 rounds off its west coast into the Yellow Sea, according to South Korea’s Joint Chiefs of Staff. While the artillery shells fell into the water north of the disputed sea border known as the Northern Limit Line (NLL), the shelling triggered warnings on South Korea’s Baengnyeong and Yeonpyeong islands, where residents were told to seek shelter as a precautionary measure. South Korea’s military responded with its own…