SEOUL - South Korea and Japan are jointly investigating whether a South Korean fishing boa  violated a Japanese exclusive economic zone near disputed islands, roughly equidistant from both countries, officials said on Wednesday.

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A Korea Coastguard official said a South Korean and Japanese coastguard vessels had been sent to the area to investigate the incident.

Assertions of Japanese sovereignty over the islands, known  as Dokdo in South Korea and Takeshima in Japan, have in the  past sparked protests in South Korea, where bitter memories linger of Japan's 1910-1945 colonisation of the peninsula.

South Korea's Yonhap news agency said the patrol boats had been involved in a standoff, but Japanese Coastguard spokesman Masahiro Ichijo played down the report, saying: "Nothing is going on at Takeshima."

Yonhap said the incident involving a 29-ton fishing boat  had taken place in waters about 70 km (45 miles) southwest of  the islands.