TOKYO, September 15. /TASS/. Four patrol ships of China’s Coast Guard have entered a zone, considered its maritime territory by Japan, near the disputed Senkaku (Diaoyu) Islands in the East China Sea, Kyodo reported.

It is noted that Japanese authorities are actively monitoring the situation and gathering information on the incident.

According to the news agency, in the late afternoon, the Chinese ships left the zone one by one having spent there about two hours.

Tensions between China and Japan over Senkaku flared up after in September 2012, Tokyo announced that it was buying the islands from their private owners. Mass anti-Japanese rallies were held in China after that. Since then, Chinese ships have constantly remained in the proximity of the disputed islands, occasionally entering the coastal zone.