S. Korea conducts live-fire drills on border islands

(ATTN: UPDATES throughout with end of drills, quotes, photos; TRIMS some previous quotes; AMENDS headline)
SEOUL, May 3 (Yonhap) -- South Korean marines staged live-fire artillery drills on Tuesday on two islands near the Yellow Sea border with North Korea, including one island bombarded by the North last November, military officials said.
The two-hour drills on Yeonpyeong and Baengnyeong islands were observed by about 10 U.S. military personnel, an official at the South's Marine Corps said.
"The drills, aimed at increasing our military readiness and purely defensive in nature, ended at around 3:30 p.m.," the official said on the condition of anonymity.
Tensions on the Korean Peninsula remain high following the North's shelling of Yeonpyeong that killed two South Korean marines and two civilians.
The North claimed its artillery barrage was in retaliation for live-fire drills by the South, while Seoul blamed Pyongyang for a premeditated attack, saying the drills were routine and no shells landed in the North's territory.
Tuesday's drills were the third live-fire exercises on Yeonpyeong since the North's bombardment. The previous drills took place without incident in spite of threats of a retaliation from the North.
Earlier in the day, the Marine official said the U.S. military personnel joined the drills to check conditions for an upcoming joint maneuver with South Korean forces.
An official at the U.S. Forces Korea (USFK), who also declined to be named, said the U.S. military in South Korea sent the observers to "enhance the tactical interoperability" with South Korean troops.
South Korean and U.S. forces are planning to conduct a joint drill on Baengnyeong Island within the coming weeks, according to officials at the South's defense ministry.
Marines stationed at the two islands fired K-9 self-propelled howitzers, Vulcan cannons and 81-millimeter mortars during Tuesday's drills, according to the Marine official.
About 28,500 U.S. troops are stationed in the South, a legacy of the 1950-53 Korean War.