TOKYO (Reuters) - Japan’s fighter jet scrambles against Chinese planes more than doubled in the first three months of the year, underscoring a “tougher security environment”, the Defence Ministry said on Friday.

Japanese combat planes scrambled 198 times to prevent possible incursions by Chinese planes, up from 93 times from January to March last year.

In the year that ended on March 31, such scrambles rose 23 percent from a year earlier to a record 571.

“The numbers of scrambles alone do not tell the whole story, but we should recognize that the increase ... indicates a tougher security environment,” Kazuhiko Fukuda, head of public affairs at the Japanese Self-Defence Forces’ Joint Staff, told reporters.

“China is modernizing its air force and is clearly aiming to improve its air combat capability in faraway skies ... Concrete activities based on those targets are reflected in these numbers.”

Japan’s ties with China have been strained by a dispute over a group of tiny East China Sea islands, regional rivalry and the legacy of Japan’s World War Two aggression.

Patrol ships and fighter jets routinely shadow each other near the uninhabited islets that are controlled by Japan, raising concern that an unintended collision or other accidents could develop into a larger clash.

China also claims almost the entire South China Sea, believed to have huge deposits of oil and gas. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims to parts of the waters, through which about $5 trillion in trade is shipped every year.