North Korea has for years lobbed missiles into Japan’s waters without great incident. But for an increasingly powerful and aggressive China to do the same — as it did Thursday as a part of military exercises — has sharply raised concerns in political and security circles from Tokyo to Washington.

Beijing’s firing of five missiles into Japanese waters to the east of Taiwan has sent a warning to both the United States and Japan about coming to the aid of Taiwan in the event of a conflict there, analysts said.

Beijing wants to remind Washington that it can strike not only Taiwan, but also American bases in the region, such as Kadena air base on Okinawa, as well as any marine invasion forces, said Thomas G. Mahnken, a former Pentagon official who is now president of the Center for Strategic and Budgetary Assessments in Washington.

It also reminds the Japanese that the American military presence on Okinawa makes Japan a target, he added.

Daniel Sneider, an expert on Japan’s foreign relations at Stanford University, said the Chinese “want to demonstrate that they have the capability to impose a blockade on Taiwan, and they want to send a very clear message to those that would come to the aid of Taiwan — the U.S. and Japan — that they can target them as well.”