Chinese maritime vessels approached the group of Senkaku / Diaoyu islands in dispute with Japan in the East China Sea for 30 hours before withdrawing.

The Japan Coast Guard (JCG) said a number of Chinese maritime patrol boats entered the 12-nautical-mile area around the disputed Senkaku / Diaoyu Island group last week.

"This is the longest Japanese invasion of Chinese ships since the Japanese government bought some of the Senkaku island group from its private owner in 2012," JCG said.

The Senkaku / Diaoyu Islands group is located in the East China Sea, where China unilaterally imposed an air defense identification zone (ADIZ) in 2013. Sino-Japanese tensions around the island group are heating up amid ongoing China.

The latest round of China's disputed island group comes as Japan's ruling Liberal Democratic Party (LDP) debates foreign policy with Beijing.

A group of LDP MPs called last week for Prime Minister Shinzo Abe's government to cancel Chinese President Xi Jinping's state visit to Japan.

Expert Ankit Panda of Diplomat Risk Intelligence said that the patrol of vessels around the Senkaku / Diaoyu Islands is part of China's calculations, taking place simultaneously with Beijing's "aggression attitude" on most baked goods.

"As usual, this is China's continuous effort to assert sovereignty around the disputed island group by making its presence here noticeable. However, Japan will not seem

Location of Senkaku / Diaoyu Island group.