Senkaku/Diaoyu islands. (Photo: Kyodo/VNA)

NHK cited a JCG source that the Chinese ships entered the waters off the Senkaku Islands (known as Diaoyu Islands in China) in the East China Sea at 4 p.m. on Thursday and left at 10 p.m. on Friday. They entered the area again at 2 a.m. on Saturday and left 39 hours later.

The Coast Guard says it was the longest intrusion into the territorial waters by Chinese ships since the Japanese government purchased some of the Senkaku Islands from a private Japanese owner in 2012.