Japan's rapid military buildup is worrying residents of the Okinawan islands close to Taiwan, the prefecture's governor said Thursday, further straining already fraught ties between the region and the government of Prime Minister Fumio Kishida in Tokyo.

Kishida unveiled a plan in December to double Japan's defense spending over five years in a bid to deter China from using military force against Taiwan that could also threaten its territory.

Much of that buildup will be in Okinawa Prefecture, which has been at odds with the central government for decades for allowing a heavy U.S. military presence there.