South Korea's coastguard said on Tuesday it had stepped up patrols near islands at the centre of a territorial dispute with Japan, a day after Seoul recalled its ambassador in anger at new Japanese claims to the rocky outcrops.

The fight over the desolate islands, known as Dokdo in Korean and Takeshima in Japanese, has been a persistent irritant in relations between the neighbours, rekindling memories in South Korea of Japan's 1910-1945 colonial rule over the peninsula.

"We're beefing up security measures in relation to Japan's decision to describe Dokdo as its territory in its textbooks," a coastguard official said.

On Monday, Tokyo said it had told Seoul that it would refer in a middle school teaching guide to the islands as Japanese territory, triggering angry rallies outside Japan's embassy in Seoul and official protests from South Korea's government.

"As a preventive measure against any possible attempt by Japanese right-wing elements sailing to Dokdo, the coastguard has strengthened our early warning system," the coastguard said separately in a statement.

The islands are controlled by South Korea, which keeps a police presence there, and lie roughly equidistant from the mainland of both countries.

The surrounding waters are popular with squid fishermen while the seabed in the area may have deposits of a natural gas hydrate that could be worth billions of dollars.

Japanese government spokesman Nobutaka Machimura on Tuesday called for a calm response to overcome differences.

"Right now Japan and South Korea have entered a new age, and efforts should be made not to interrupt this," he said.

South Korean President Lee Myung-bak, who took office in February, pledged to better ties with major trading partner Japan after his predecessor Roh Moo-hyun tried to score points at home by fanning the flames of lingering anti-Japan sentiment.

Analysts said that while South Koreans may rally around the flag in this dispute, they may not rally around Lee.

"People tend to regard the Dokdo case as his diplomatic mistake or failure. Even though people are united against Japan, it is not likely to boost his popularity," said Kang Won-taek, a political science professor at Soongsil University in Seoul.

The public is likely to see his call to get closer to Tokyo as just one more policy blunder for his new government, which has seen its support rate fall after bungling a U.S. beef deal and personnel appointments, Kang said.

Apart from the spat with South Korea over the islands, Japan also has separate territorial fights over different sets of islands with Russia, China and Taiwan.