Photo/IllutrationSome of the Senkaku Islands, from foreground, Minami-Kojima, Kita-Kojima and Uotsurishima islands (Asahi Shimbun file photo)

BEIJING--China seems determined to keep rattling Japan and the United States over the disputed Senkaku Islands in the East China Sea, but not to the point of an all-out confrontation.

Its latest ploy was to dispatch a Navy warship to a contiguous zone just outside Japanese territorial waters around the islands early on June 9, the first time for it to undertake such action.

It now turns out that China has been sending remodeled warships into territorial waters around the Senkakus for some time.

The vessels were converted for use by the China Coast Guard, but at least one was found equipped with autocannons.

Three ships operated by the China Coast Guard entered Japanese territorial waters around the uninhabited Senkakus on June 8. China chose to view matters differently, saying the coast guard ships were patrolling the waters off the Diaoyu Islands, the name used by Beijing to refer to the Senkakus.

It also revealed the names of the three ships.

According to sources, one of those ships, China Coast Guard vessel 31241, was a former warship known as the 541 Huaibei destroyer that belonged to the PLA (People's Liberation Army) Navy East Sea Fleet.

Converted Chinese Navy ships have been entering territorial waters around the Senkakus since late last year when international attention was focused on the South China Sea and China's efforts to strengthen its military presence there while the U.S. Navy pushed ahead with its "freedom-of-navigation operations" in those same waters.

According to sources, one of the three Chinese government ships that entered territorial waters around the Senkakus last Dec. 26 was China Coast Guard vessel 31239, which was armed with four 37-millimeter autocannons.

That ship was originally the 539 Anqing destroyer that belonged to the East Sea Fleet. The exterior had been repainted white as part of the process of converting it for coast guard use.

The revelation that the former warship had entered Japanese territorial waters sent shock waves through the government.

Sources said at least three Chinese Navy warships have been converted into government ships. The China Coast Guard vessels 31239 and 31241 have been dispatched to waters near the Senkakus on a rotating basis.

A former high-ranking official with the Chinese Defense Ministry said of those converted vessels, "They are equipped differently from warships as radar and other equipment have been removed."