Rhetoric regarding two sets of disputed islands in the Pacific Ocean has become markedly more aggressive as Japan warns China and South Korea to keep away from territories it claims as its own.

Authorities in Japan said Friday that they would not tolerate South Korea’s “illegal occupation†of Takeshima -- the Japanese name for a series of rocky islets peppering the Sea of Japan.

Japanese officials have also chided China over nearby islands in the East China Sea, accusing the nation of allowing activists to land on the island chain earlier this month.

The disputed East China Sea chain is known as Senkaku in Japan and Diaoyu in China.

“A series of incidents have occurred, threatening to violate our sovereignty, which we find extremely regrettable. We do not tolerate these actions," Japan’s Prime Minister Yoshihiko Noda told reporters earlier this month.

The stern reproach comes after South Korean President Lee Myung-bak visited the Sea of Japan islets, prompting Japanese lawmakers to pass symbolic resolutions condemning his visit.

Noda argued that Lee “illegally landed†on the disputed islands.

Meanwhile, Japan officials continue to fume after Chinese activists travelled from Hong Kong to the disputed East China Sea island chain, which is controlled by Japan but also claimed by China.

The islands, while barren, are located near important waterways. The chain is also surrounded by fishing grounds and is potentially close to untouched natural resources.

Japanese officials arrested all 14 of the Chinese activists for illegal entry onto the islands, triggering anti-Japan protests in Chinese cities and calls to boycott Japanese products.

The activists were out of custody two days later and deported.

Turning the tables, ten Japanese activists landed on an island in the East China Sea chain last week and raised flags on the territory. The action triggered protests in China and prompted Beijing officials to complain to authorities in Tokyo.

Japanese Vice Foreign Minister Kenichiro Sasae reportedly told China’s ambassador to Japan that the protests in China were “regrettable.â€

Noda has pledged to strengthen patrols near the disputed islands, but Chinese activists say they have not been discouraged and are preparing for another confrontation.

Activist Li Nan said he predicts the age-old dispute likely won’t be resolved at the negotiating table.

“I don’t think it’ll be solved by diplomacy,†he told Â鶹´«Ã½. “That leaves action, even weapons.â€

Noda has come under pressure to take a firmer stance over the disputed islands, but his recent words mark some of the strongest language used since the disagreement began.

What’s more, Tokyo’s nationalist governor Shintaro Ishihara has said he wants to visit the disputed East China Sea chain in October, saying he doesn’t care if he gets arrested.

It’s anticipated that the visit, during which Ishihara is expected to accompany a survey of the islands, could trigger significant backlash.

With a report from Â鶹´«Ã½â€™ Beijing Bureau Chief Janis Mackey Frayer and files from The Associated Press