Image copyright AP Image caption The boat sailed from Hong Kong with a group of activists on board

Japanese police have arrested 14 pro-China activists who landed on disputed islands, reports say.

The group had sailed from Hong Kong to the islands, known as Senkaku in Japan and Diaoyu in China, followed by Japanese coastguard vessels.

China called for the activists' immediate and unconditional release.

Japan is also embroiled in a dispute with South Korea about another island group, as well as a high-level visit to the controversial Yasukuni shrine.

The various rows erupted as Japan marked the anniversary of its surrender at the end of World War II and South Korea its independence from Japanese colonial rule.

The group of pro-China activists set sail on Sunday.

Japanese coastguard vessels surrounded the boat as it approached, but seven of the activists jumped overboard and swam to one of the islands, local media report.

Japan-China disputed islands Image copyright AP The archipelago consists of five islands and three reefs

Japan, China and Taiwan claim them; they are controlled by Japan and form part of Okinawa prefecture

Japanese businessman Kunioki Kurihara owns three of the islands, which he rents out to the Japanese state

The islands were the focus of a major diplomatic row between Japan and China in 2010 Q&A: China-Japan islands row

Officials told the BBC that two activists returned to the boat, while the other five were arrested on land.

Later, the coastguard said the two activists who returned and seven more who had remained on the boat had been arrested for "alleged illegal entry".

It is the first time non-Japanese nationals have landed on the disputed islands since 2004.

A spokesman for the group said they wanted the world to know "that this is - way back in history - the territory of China".

"The Japanese have no right to stop us," David Ko told the Associated Press from Hong Kong.

Chief Cabinet Secretary Osamu Fujimura said Japan had lodged a diplomatic protest with China and in Hong Kong over the activists.

A foreign ministry spokesman had earlier warned Japan not to "endanger" the activists and said Beijing was ''paying close attention'' to the developments, Xinhua said.

Shrine visit

Tensions between China and Japan have been rumbling in recent months over the islands in the East China Sea.

Taiwan also claims the Senkaku or Diaoyu islands, which are controlled by Japan and form part of Okinawa prefecture.

Japan-S Korea disputed islands Image copyright Reuters Known as Dokdo (Solitary islands) in Korea, Takeshima (Bamboo islands) in Japan

Also known as Liancourt rocks

Claimed by Japan and South Korea, but occupied by South Korea since 1954

Just 230,000 sq m in size

But surrounding waters valuable for their fishing Profile: Dokdo/Takeshima islands

Largely uninhabited, they are close to strategically important shipping lanes, offer rich fishing grounds and are thought to contain oil deposits.

In September 2010, relations between China and Japan plummeted after the arrest of a Chinese trawler captain near the islands. The captain was accused of ramming two Japanese patrol vessels in the area, but Japan eventually dropped the charges against him.

In April a fresh row ensued after Tokyo Governor Shintaro Ishihara said he would use public money to buy the islands from the current private owner.

Meanwhile, a group of South Koreans finished a relay swim early on Wednesday to another group of islands claimed by Japan.

It followed the first-ever visit of a South Korean president to the islands - called Dokdo by South Korea and Takeshima in Japan - on Friday.

President Lee Myung-bak's visit has infuriated Japan, which recalled its ambassador to South Korea. Mr Lee, meanwhile, on Wednesday hit out at Japan for failing to heal historical wounds.

And in Japan, ministers Jin Matsubara and Yuichiro Hata paid what they said were private visits to the Yasukuni Shrine to mark the end of WW II, despite Prime Minister Yoshihiko Noda urging members of his cabinet not to do so.

The shrine is dedicated to Japan's war dead, including war criminals, and is viewed by many of the country's neighbours as a reminder of Japan's military past.

Both China and South Korea have protested against the visit.