Japan defied South Korean protests Wednesday and dispatched two ships to begin a maritime survey near disputed islets between the two nations, raising the stakes in the territorial standoff.

South Korea earlier had dispatched a flotilla of patrol boats to guard the territory, held by Seoul but claimed by Tokyo.

Two Japanese survey vessels left Sakaiminato on Wednesday, headed for the islands, said Yuzuru Kubota, a coast guard official in the port city on Japan's west coast.

But he said the ships were lingering just beyond the bay and were not steaming immediately toward the survey area. Japan has refused to provide a schedule; news reports said the survey could start as soon as Thursday.

South Korean Foreign Minister Ban Ki-moon warned Japan not to go ahead, saying his country — which has long protested Japan's repeated claims to the islets — was preparing for "all scenarios" in the dispute.

South Korean local media have reported that Seoul may try to capture Japanese vessels entering disputed waters.

"If Japan pushes ahead ... we will react sternly to it in accordance with international and domestic laws," Ban told a nationally televised news conference. "The responsibility for all problems caused by this lies with Japan."

"The government is preparing countermeasures for all scenarios," Ban said without elaborating. He spoke after President Roh Moo-hyun held a sudden meeting with security ministers to discuss the dispute.

Later in the day, the South Korean parliament approved a resolution calling for a halt to the survey.

Ban's comments came after Roh on Tuesday called the survey, expected to last through the end of June, an "offensive provocation."

Japan, however, has flatly refused to abandon the project. Chief Cabinet Secretary Shinzo Abe said on Wednesday that Japan's right to the study was protected under international law.

"I would like the South Korean side to understand this point well," Abe told reporters. "Japan will calmly proceed with its activities in line with international law."

Kubota, the Japanese coast guard official, refused to provide full details of the survey, but said the area covered comprised of a vast rectangle just north of the disputed islands.

He refused to say how close the ships would come to the outcroppings, but he said it rested completely within Japan's exclusive economic zone according to the U.N. Convention on the Law of the Sea.

The bluster on both sides, however, was coupled with calls to find a diplomatic solution to the impasse. The two countries have sparred repeatedly in recent years over the islets, which rise from waters rich in fish and other national resources.

The dispute flared recently when Japan's Education Ministry edited public school textbooks to say the volcanic outcroppings belong to Japan. Seoul's ambassador to Japan issued a formal complaint over the change.

The surveys are aimed at collecting hydrographic data. Japan's Sankei and Asahi newspapers said the boats — 621-ton Meiyo and 605-ton Kaiyo — were to collect data before an international conference on ocean floor topography in June in Germany.

At the conference, South Korea was expected to propose its own name for the area surrounding the islets, the papers said. South Korea prefers the "East Sea" to the "Sea of Japan," as it is known internationally.

Japan's survey comes after South Korea conducted a similar study. Japanese officials say Seoul's research was part of its effort to change the body of water's name, but South Korean officials deny that is their aim.

The island tiff comes amid rocky relations between the two Asian neighbors.

South Korea, which nurses angry memories of Japan's harsh 1910-1945 colonization of the Korean Peninsula, has fervently objected to Japanese Prime Minister Junichiro Koizumi's repeated visits to a Tokyo war shrine considered by critics to be a glorification of Japanese militarism.

Roh canceled a scheduled summit with Koizumi last year because of the shrine visits and later avoided a customary one-on-one meeting with the Japanese leader on the sidelines of a regional conference.

South Korea's ambassador to Japan, Ra Jong-il, said that he'd seen relations between the two countries deteriorate in the two years since he arrived in Tokyo.

"This problem is another example of Japan's long-standing attempt to distort history, and the problem must be resolved comprehensively," he told reporters at the Japan Press Club.

Despite the political tension, however, economic and other exchanges between the two countries have remained intact and the two sides have also cooperated closely to resolve the dispute over North Korea's nuclear program.