The Japanese coastguard says three Chinese ships have entered disputed waters off Japanese-controlled islands in the East China Sea.
It's the first such incursion this year.
The Chinese coastguard vessels sailed into the 12-nautical-mile territorial waters off one of the Senkaku islands on Sunday afternoon.
Both countries have a claim on the islands.
The ships left less than two hours later.
Chinese state-owned ships and aircraft have approached the Senkakus on and off to demonstrate Beijing's territorial claims, especially after Japan nationalised some of the islands in September 2012.
Sunday's intrusion was the first since 29 December 2013 when three Chinese coastguard ships entered the zone and stayed for about three hours.
