South Korea's Foreign Ministry called in China's Ambassador Zhang Xinsen to warn about Beijing making claims that Ieodo Island is within China's exclusive economic zone, a report in The Korea Herald newspaper said.
Kim Jae-shin, South Korea's deputy minister for political affairs, reiterated South Korea's claim to Ieodo, saying that it was much closer to South Korea than mainland China, the Herald report said.
In 1987, South Korea placed a shipping warning beacon over the disputed submerged rock, then called Socotra Rock.
Socotra was renamed Ieodo in 2001 when Seoul built an oceanographic research platform over it, complete with helipad.
But China has claimed the rock, called Parangdo, as being within its EEZ, although it is around 200 nautical miles from the mainland.
Seoul refutes Beijing's claim, pointing out Ieodo lies less than 100 miles south of Marado, a treeless island of less than 1 square mile and home to around 90 people. Marado is about 5 miles off the south coast of South Korea's Jeju island, a favorite South Korean holiday destination.
China's claim should be "a wake-up call to South Korea, which has focused primarily on deterring North Korea while paying less attention to possible maritime threats from neighboring states such as China and Japan," the report in The Korea Herald said.
Of particular concern should be China's growing naval presence, including recent sea trials of its first aircraft carrier Varyag which Beijing bought from Ukraine in 1998.
"As China is to commission its first aircraft carrier in the near future, we now face the reality of how to deal with such developments," said Lim Han-kyu, adjunct professor at Hyupsung University.
"Our concerns (about China's expanding naval might) are becoming a reality," said Lim, who served as vice chief of the South Korea's Naval Education and Training Command from 2006-07.
He said Seoul needs to invest in more coast guard vessels capable of spending long periods at sea.
In December, South Korean President Lee Myung-bak called for "strong" measures to protect the country's coast guard sailors during the crackdown on illegal fishing by Chinese boats.
More equipment and personnel may be allocated to the coast guard service so there is no repeat of the fatal attack on two sailors during a raid on a Chinese boat suspected of fishing illegally in South Korean waters, he said.
Lee's remarks came after a coast guard officer was allegedly stabbed by the captain of the Chinese fishing boat and died shortly after in hospital. Another coast guard member also was stabbed in the incident, a report by the South Korean news agency Yonhap said at the time.
Also last month, the Philippines, which also has disputes with China over islands, announced its navy would soon receive its second decommissioned U.S. Coast Guard ship, the USCGC Dallas, a Hamilton class cutter 378 foot-long, 3,250-ton vessel.
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