TOKYO (AFP) - Three Chinese government ships remained in the waters off disputed Tokyo-controlled islands for nearly 12 hours on Monday, Japan's coastguard said, as a long-running row shows no sign of fading.

Maritime surveillance vessels were spotted in the 12-nautical-mile zone off the Senkaku islands, which China calls the Diaoyus, in the East China Sea shortly after 9:00 am (0000 GMT), the coastguard said. They left the zone shortly before 9:00 pm.

It is the latest episode in a fraught few months which have seen repeated stand-offs between official ships from both sides as they jostle over ownership of the strategically-important and resource-rich islands.

In a separate maritime incident in the East China Sea, a foreign submarine was spotted sailing underwater near Kume, one of Japan's Okinawan islands, from late Sunday to early Monday, the Defence Ministry said.

The submarine was thought to be Chinese, Japanese media said.

It sailed close to 12-nautical-mile territorial waters off Kume, alarming Japanese officials, although it did not violate international law.

"The situation is worth attention," Chief Cabinet Secretary Yoshihide Suga told a regular press briefing, noting that a foreign submarine was also spotted on May 2 near the Japanese island of Amami on the fringe of the East China Sea.

Defence Minister Itsunori Onodera said the self-defence forces would demand that the submarine seen in the latest incident should come to the surface and show the flag of its nationality if it enters Japan's territorial waters.

Asked about the three Chinese ships, US State Department spokeswoman Jen Psaki said Washington did not take a position on "the question of ultimate sovereignty over the islands".

"We do urge all parties to avoid actions that could raise tensions or result in miscalculations that would undermine peace, security and economic growth in this vital part of the world," she said.

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Chinese ships in disputed-islands waters: Japan