Two Chinese government ships sailed into the waters of disputed Tokyo-controlled islands on Saturday, Japan's coastguard said.

The surveillance ships entered the 12-nautical-mile zone around the Senkakus, which Beijing claims and calls the Diaoyus, shortly before 1:00 pm (0400 GMT), the coastguard said.

Chinese government ships have frequently spent time around the disputed island chain since Tokyo nationalised three of the islands last September.

The islands are also claimed by Taiwan.