Japan has increased security around a group of disputed islands it nationalized one year ago Wednesday amid strong protests from China, which also claims them and has been stepping up patrols of its own.
Tokyo and Beijing are at odds over the uninhabited islands in the East China Sea, called Senkaku in Japanese and Diaoyutai in Chinese.
Wednesday marks the first anniversary of Japan's purchase of several of the islands from their private owners — a sale China says was invalid. Both countries have since regularly sent coast guard vessels and aircraft to the area to assert their competing claims.
Japanese Defense Minister Itsunori Onodera said surveillance had been increased in the area for the anniversary, but did provide details. No incidents were reported as of early Wednesday afternoon.
The standoff, which shows no sign of abating, has deeply damaged diplomatic relations between the two Asian powers and heightened concerns of a possible military clash.
Japan lodged a protest after eight Chinese vessels on Tuesday briefly entered waters Tokyo claims near the islands. On Monday, Japanese fighter jets were scrambled when a Chinese military aircraft believed to be a drone was spotted. Though the drone remained in international airspace, Japanese officials expressed concern about the increased activity.
So far, Tokyo and Beijing have been careful to calibrate their actions to avoid a direct military conflict.
But with neither side backing down or wanting to look weak, the dispute continues to simmer. In a statement that appeared to up the ante, Japanese Chief Cabinet Secretary Yoshihide Suga said Tuesday that Tokyo considered deploying personnel to the islands an option.
No one currently lives on the islands, and China immediately slammed the remarks as provocative.
"If they do provoke, they must be prepared to take the consequences," Chinese Foreign Ministry spokesman Hong Lei said Tuesday in Beijing.
Stationing public servants on the islands was a campaign promise made by Prime Minister Shinzo Abe's hawkish ruling party, which is also pushing to give Japan's military a more assertive role in international peacekeeping and in stepping up territorial defenses.
The islands, also claimed by Taiwan, are about 2,000 kilometers (1,240 miles) southwest of Tokyo.
Japan' coast guard said there have been more than 200 intrusions by foreign vessels into Japanese-claimed waters near the islands in the past year.