Beijing: China on Thursday called for "concrete actions" from Japan to resolve a bitter row over Tokyo`s arrest of a Chinese boat captain in disputed waters, which Beijing called an "obstacle" in ties.
"It is an obstacle in bilateral relations at present and we hope Japan will take concrete actions to eliminate the obstacle," Foreign Ministry spokeswoman Jiang Yu told reporters.
"Japan should return the captain immediately to avoid further detriment to bilateral relations."
Japan has warned its nationals living in China to be vigilant, an embassy official said on Thursday, ahead of possible protests over Tokyo`s arrest of a Chinese boat captain in disputed waters.
Beijing and Tokyo are entangled in their worst diplomatic spat in years, stemming from the collision last week of a Chinese fishing trawler and two Japanese coastguard vessels near a disputed island chain in the East China Sea.
China has so far summoned Japan`s ambassador five times over the incident and demanded the captain`s unconditional release. Tokyo says the skipper intentionally rammed the Japanese vessels during a high-seas chase.
Anti-Japanese protesters are planning demonstrations at the weekend in Beijing and Shanghai, reports say, prompting Tokyo`s embassy to urge nationals living or working in China to take heed.
"We warned Japanese nationals living in China as well as those travelling and doing business here, through emails and our website, that they should take care of their safety," an embassy press officer said.
The Japanese official, who asked not to be named, said the embassy had no specific information that a demonstration would take place outside the mission on Saturday, and had received no guidance from Chinese police.
A notice posted on the embassy`s website said police had told Tokyo they would "do their utmost to ensure the safety of Japanese nationals".
The statement, dated Wednesday, urged Japanese citizens living in China to "use caution in words and attitude when engaging with Chinese individuals" and refrain from carrying out "noticeably provocative actions".
China`s state Global Times newspaper quoted Li Nan, a member of the China Federation of Defending the Diaoyu Islands, as saying his group was considering weekend demonstrations.
A posting in a chatroom of the group`s website called for a protest outside the Japanese consulate in Shanghai on Saturday morning.
The uninhabited islands -- called Senkaku in Japan and Diaoyu in China -- lie in an area with rich fishing grounds that is also believed to contain oil and gas deposits, and which has been a frequent focus of regional tensions.
China, Japan and Taiwan all claim the islands.
Beijing has already postponed talks with Tokyo on joint energy exploration in the East China Sea and scrapped a trip to Japan by a senior lawmaker in protest, branding the skipper`s arrest "illegal".
Tokyo has called the situation "extremely regrettable" and said there were no plans for the prime ministers of China and Japan, the world`s number two and three economies, to meet next week on the sidelines of a UN summit in New York.
"Nothing is decided at this point. Both sides have made no active efforts to set up such a meeting," Japan`s top government spokesman Yoshito Sengoku said, asked if the bilateral meeting will be held in New York.
The United States has weighed in on the deepening diplomatic spat, urging both sides to resolve the matter through dialogue.
Ties between China and Japan had steadily warmed since 2006, when they began to put behind decades of distrust stemming largely from Japan`s wartime invasion of China. They already have a deep trade and economic relationship.