Japan is vowing to take steps to strengthen its claims over two sets of islands that are already causing tensions with its neighbors, according to AP. Japan's relations with Seoul have rapidly deteriorated since South Korean President Lee Myung-bak visited tiny islets in the Sea of Japan this month to push his country's claim to them. Days later, a boatful of Chinese activists landed on a group of East China Sea islands claimed by Japan, China and Taiwan. In resolutions adopted by Parliament Friday, Japan called the actions by China and South Korea "extremely regrettable." Prime Minister Yoshihiko Noda says Japan will strengthen security around the East China Sea islands to prevent future landing attempts. He also sent Lee a protest letter, which Seoul rejected.