News- World: Chinese coast guards have staged patrols around the disputed islands in the East China Sea, causing anger among Japanese government officials and prompting Tokyo to lodge an official complaint with Beijing.

Four Chinese vessels that were believed to be armed approached Japanese-controlled disputed islands in the East China Sea on Friday, Tokyo government's spokesman told reporters at a press conference.

The incident was "the first time four (Chinese) ships carrying what appear to be cannons entered Japanese territorial waters" around the Senkaku islands also called in China as Diaoyu Islands, in the East China Sea, according to Yoshimasa Hayashi.

"I am not in a position to state what the Chinese side's intentions are, but the intrusion of vessels belonging to China's coastguard into (our) territory is a breach of international law," the Chief Cabinet Secretary said.

Tokyo lodged a "strong protest" through diplomatic channels calling for a swift exit from the area, Hayashi said. The four vessels stayed in the area for more than an hour and left shortly after midday, he said.

"The intrusion into our territorial waters is extremely regrettable and cannot be tolerated. We will continue to do our utmost to be vigilant and monitor the areas surrounding the Senkaku Islands with a sense of urgency, while dealing calmly and resolutely with China," Hayashi said.

For their part, China's coast guard said the patrols were a "routine action" to safeguard sovereignty, security and maritime rights.

It is a "necessary step" for peace and stability as well a response to recent "negative moves", it said. "We advise the Japanese side to be prudent in its words and actions, to reflect on it and to stop provocations."

China’s coast guard will step up its "law enforcement efforts," it added,

Beijing has territorial disputes with the nearby countries in the East China Sea and South China Sea.

In this regard, Beijing has issued warnings, saying it will not allow the violation of Chinese territorial waters, or secession in any Chinese land.