Japan is to stage amphibious landing drills in the East China Sea, coinciding with wargames Russia and China are holding near islands at the centre of a Tokyo-Beijing territorial row.
About 1,330 personnel, four naval vessels and aircraft from Japan's three services will be involved in exercises in the Amami group of islands and in waters east of Okinawa, the defence ministry said in a press release, adding they were intended to bolster Japan's ability to "defend islands".
The statement was issued on Thursday hours after China's state media, quoting the country's defence ministry, said the Chinese and Russian navies will stage joint exercises "off Shanghai" in late May.
The naval exercises will take place in waters northwest of the Japanese-controlled Senkaku islands, which China also claims and calls the Diaoyus, Chinese media said, quoting a Russian radio report.
On Friday, three Chinese coastguard ships sailed inside territorial waters off the disputed islands for about three hours, being chased by Japanese patrols.
It was the third such incursion since US President Barack Obama vigorously reasserted on April 24 that Washington would defend Japan under a bilateral military treaty if China initiated an attack in the tense dispute.
China has already dismissed Obama's position, saying that the islands are "China's inherent territory".
Chinese ships have regularly approached these islands -- thought to harbour natural resources -- since Japan nationalised some of them in September 2012, reigniting a long-running territorial dispute.
The Japanese landing drills "to defend and recapture islands" run from May 10 to 27 and will focus on the tiny uninhabited isle of Eniya off Amami Oshima island, according to media reports.
"The Defence Ministry has been strengthening the capabilities of amphibious operations in response to China's maritime advances," the Kyodo news agency said, "and the landing drills in the Amami islands are seen as a move to keep China in check".
The joint Russian-Chinese drills were officially described as "regular exercises" and come after the two countries held similar manoeuvres in July last year off Vladivostok on Russia's Far East coast.
In April 2012, the two navies staged joint drills in the Yellow Sea.
China may want to use the joint drills to demonstrate its coordination with Russia in the East China Sea and keep Japan and the United States in check, Kyodo reported.
A Japanese defence ministry official told AFP, "China is widely seen to have used such drills in boosting its navy's operational capability."
The official, charged with policy research, said he could not tell if the upcoming drills were linked to the island dispute.
"But if naval capability improves overall, it may be useful for China in various areas such as its relations with Taiwan and its operations in the East China Sea and the South China Sea."