Ten Chinese surveillance ships sailed into the contiguous zone off the Senkaku Islands on Tuesday afternoon, following a similar incursion by a fishery monitoring ship in the morning, Chief Cabinet Secretary Osamu Fujimura said. However, Fujimura said the government had not confirmed the arrival of about 1,000 fishing boats that Chinese media reported had left several ports Monday for waters near the Senkaku islets.

"We haven't confirmed whether a large number of fishing boats" are in the area, Fujimura said at a press conference Tuesday afternoon.

This incident came just days after six surveillance ships of China's State Oceanic Administration entered Japanese waters around the islands. The Japan Coast Guard had described last week's incursion as "unprecedented."

According to the JCG, a patrol vessel confirmed a Chinese fishery monitoring ship was inside the contiguous zone, about 43 kilometers north-northwest of Uotsurijima, one of the five Senkaku Islands, at about 6:50 a.m.

The Yuzheng vessel belongs to the Chinese Agriculture Ministry's Fisheries Bureau.

According to the JCG and its 11th Regional Coast Guard Headquarters in Naha, the Chinese ship sailed eastward through the zone, north of Kubashima island, which is about 27 kilometers from Uotsurijima. The ship then changed course to head northwest and reentered the contiguous zone off Kubashima at about 12:15 p.m. No other Chinese fishery monitoring vessels or private fishing boats were spotted nearby, they said.

The contiguous zone is a 22-kilometer strip of water extending from the outer edge of Japanese waters.