China is refitting five more former warships as armed coast guard vessels with the aim of deploying them in disputed waters, a Hong Kong-based watchdog said Monday. Deployments may include near the Japan-held Senkaku Islands.

The Information Center for Human Rights and Democracy quoted sources as saying refits of three Jiangwei-class guided-missile frigates are now complete, while ongoing work on two Luda-class guided-missile destroyers will be finished within the year.

China Coast Guard vessels will be deployed not only near the Senkakus, which are known to China as Diaoyu, but also in waters near Vietnam and North Korea, the center said.

"The coast guard vessels have retained the machine-gun cannons," it said. "They can launch shrapnel shells and armor-piercing ammo and have higher speed than the original warships after slashing weight."

The report comes a day after four China Coast Guard vessels, including one armed with guns, were spotted near the Senkakus, according to the Japan Coast Guard.

The center said that one of them, the Haijing 31241, is a refitted frigate equipped with Type 76A guns of 37 mm caliber and shrapnel shell launchers, while the same goes for the Haijing 31239 seen sailing in the area on Dec. 26.

Chinese ships have often been seen in the area after the Japanese government purchased a major part of the uninhabited islands from a Japanese private landholder and put them under state control in 2012. The isles are claimed by both China and Taiwan.

Questioned on Dec. 23 about the patrols, a Chinese Foreign Ministry spokesman replied: "The equipment on Chinese coast guard vessels is standard equipment and no different from other countries' practice." He added, the patrols are "totally justified."