South Korea's Navy on Wednesday conducted a maritime drill to defend the country's easternmost islets of Dokdo in the East Sea, officials said, as Japan has laid persistent claims to the sovereign territory.

The Navy kicked off a biannual military exercise to guard Dokdo from unlawful intrusion by mobilizing its warships and maritime patrol planes, it said.

If weather conditions permit, the Marine Corps is also expected to conduct a landing drill on the islets, it said.

Since 1986, the South Korean Navy and Coast Guard have carried out joint maneuvers twice a year in waters near the islets, which lie some 87 kilometers southeast of Ulleung Island and lie closer to Korea than Japan. Japan has lodged a protest against Seoul's move.

Japan has long claimed sovereignty over Dokdo, and it is one of the thorniest diplomatic issues between the neighbors. Japan colonized the Korean Peninsula from 1910-45.

The Navy had planned to conduct an exercise to defend the islets last month when it carried out maritime drills but decided on a delay. This raised speculation that the country delayed the drill so as not to overlap the date of Seoul and Tokyo's signing of a military intelligence-sharing pact.

On Nov. 23, South Korea and Japan inked the pact in a bid to better counter North Korea's nuclear and missile threats.  (Yonhap)