China's aircraft carrier Liaoning sailed into the western Pacific on Wednesday, passing between Japan's Okinawa and Miyako islands, Japan's Defense Ministry said, Kyodo News reported.

The carrier then launched and landed fighter jets about 250 kilometers south of Ishigaki Island, Kyodo said. That area is inside Japan's exclusive economic zone, the waters where Japan has special rights over resources.

Japan's Air Self-Defense Force scrambled fighter jets in response, Kyodo and the Nikkei reported. Japanese navy ships and patrol planes kept watch. The Liaoning sailed with three Chinese missile destroyers, the Nikkei said.

It is the first time since May and June that Japan's ministry has reported on the carrier's movements, Kyodo said.

China said the trip was planned. Its defense ministry said the training is part of "the annual routine training plan," The Japan Times reported. It said the drills are "in compliance with relevant international law and practices and not directed against any specific country or target."

But the Chinese navy has been sending ships deeper into the western Pacific in recent years, which worries Tokyo, The Japan Times said. Some Japanese defense officials see the area as an exposed flank.

Last December, fighter jets from the Liaoning twice locked their radar on Japanese planes southeast of Okinawa, the paper reported. Last summer, China sent the Liaoning and another carrier deep into the Pacific.

Relations between the two countries fell to their lowest point in decades after Japanese Prime Minister Sanae Takaichi said last November that Japan could step in militarily during a crisis over Taiwan, The Japan Times said. China claims Taiwan as its own territory.

Japan says it will keep a "calm and resolute stance" while watching the waters around it, the paper reported.

What we know: The Liaoning entered the western Pacific and launched jets inside Japan's economic zone.
What we don't: How long the drills will last.