TOKYO—The Japanese government is providing more maritime equipment to its neighbors, as part of moves by U.S. regional allies to forge closer security ties in response to China’s aggressive behavior in the Western Pacific.

On Thursday, Philippine President Benigno Aquino III, who is on a state visit to Japan this week, signed a deal with a Japanese shipbuilder to buy a fleet of 10 patrol vessels. Tokyo will provide a low-interest loan worth ¥19 billion ($150 million) to pay for the ships, marking a significant shift in Japan’s...