SEOUL - South Korean Prime Minister Kim Hwang-sik expressed regret Tuesday over Japan's boycott of a South Korean air carrier following its test flight near a set of disputed islets claimed by both countries.

Japan's foreign ministry has instructed its officials not to fly with Korean Air for a month in protest against the demonstration flight last month by Korean Air's first Airbus A380 near the islets, known as Dokdo in South Korea and Takeshima in Japan.

"The Cabinet should draw up consistent long-term measures regarding Dokdo and continue our territorial control of the islets, " the prime minister said during a Cabinet meeting he presided over earlier in the day, according to his office.

Calling the boycott "very regrettable," Kim said South Koreans are also concerned about a planned visit by Japanese lawmakers to the South Korean island of Ulleung, located some 90 kilometers away from the islets in question.

His remark came after South Korea's foreign ministry demanded last week Japan immediately withdraw its measure against the Korean Air, calling its boycott "disappointing and very regrettable."

The islets in the East Sea lying halfway between South Korea and Japan has been a source of recurring diplomatic row between the two neighbors.

South Korea has maintained its effective control of the islets for decades since the end of Japan's 1910-45 colonial rule, and says the islets belong to the country "historically, geographically and by international law."