Japan Friday began a massive 18-day military exercise, which Chinese military observers say aims to bolster its ability to block the Chinese navy's passage to the West Pacific and seize the disputed Diaoyu Islands in the East China Sea.

Destroyers, fighter jets and 34,000 troops will take part in the war games in Kyushu and Okinawa.

The exercise will feature "a series of actions in defending islands" including joint operations in island landings, AFP earlier quoted Japan's defense ministry as saying.

According to the report, the air-sea-land drill will involve amphibious landings on the uninhabited atoll of Okidaitojima, 400 kilometers southeast of the main Okinawan island, and live-fire exercises involving destroyers and F-2 fighter jets will also be conducted.

The Japanese side claimed such drills have no hypothetical enemy, but Du Wenlong, a Chinese military expert, told China News Service the "first large-scale war games in areas to the southwest of Japan" are clearly aimed at the dispute over the Diaoyu Islands.

"Once there is any unexpected emergency in the area, Japan's combat operation will be the same as the drill," he said.

In addition to the island capture drill, units equipped with Type 88 surface-to-ship missiles will be deployed on Miyako Island and in the southern part of Okinawa's main island, putting all waters between the islands within range of the guided anti-ship missiles, the New York-based RTTNews reported.

Li Li, a military analyst, told news portal people.com.cn that the deployment on Miyako Island is meant to bolster its ability to block the Miyako Strait, which the Chinese navy always sails through to reach the West Pacific.

The Japanese exercise came as the People's Liberation Army (PLA) Navy concluded its drill in the West Pacific on Friday. It was one of the largest such projects in terms of participating teams and the range of exercises in recent years.

Navy Commander Wu Shengli described the drill as a success, saying that it shows China's capability and resolve in safeguarding national security and maritime interests.

The Chinese defense ministry Thursday was scathing about a Japanese vessel and aircraft that entered its drill zone disregarding a notice about the military exercise that was released in advance.

In response, Japan's Defense Minister Itsunori Onodera Friday told a press conference in Tokyo, "I don't see any problem as long as we conduct regular surveillance activities according to international law," Japan's Kyodo News reported.

"We monitored (their activities) by visual confirmation and with equipment to make sure they would not pose threats" to Japan, he said.

A source with a related Japanese government department, who asked to remain anonymous as he was not authorized to speak to the media, told the Global Times Friday that after the Chinese defense ministry made the representation to the Japanese side on Thursday, Japanese diplomats visited the defense ministry on Thursday night and conveyed Tokyo's views, insisting the Japanese Maritime Self-Defense Force's move was in line with international laws and practice.

Xing Guangmei, head of the law studies sector at the Chinese Naval Research Institute, told the Global Times the move infringed on China's rights to use the open seas granted by the UN Convention on the Law of the Sea.

"The setting-up of the live-fire drill zone was made public through the International Maritime Organization, which makes the area a restricted navigation zone in the eyes of international law. Vessels and aircraft from all countries have the obligation to avoid the area," Xing said, adding that if the Japanese warship had been accidentally hit in the area, China would not have been held responsible.

At Friday's press conference, Onodera also said, "It's important to set up a hotline between Japan and China" to avoid unnecessary worries and concerns about their activities.

The Japanese government source told the Global Times that despite the difficulties in bilateral relations, the channel for communication between the two countries' militaries are still open, and the atmosphere for such exchanges are "not tense."

Agencies contributed to this story