According to images supplied on a Pentagon information source, four Chinese warships, including one of its most sophisticated destroyers, were sighted travelling in the waters outside Alaska late last month as the Chinese navy continues to expand its range.

A fleet of four ships from China's People's Liberation Army Navy (PLAN) was recently photographed cruising towards a US Exclusive Economic Zone (EEZ) near Alaska's the Aleutian Islands, according to the US Coast Guard.

The move comes as China continues to protest the passage of the US Navy and allied ships through disputed South China Sea waterways.

The voyage was revealed by the Defence Visual Information Distribution Service website of the US military.

US defence website The Drive reported the images were shot between August 29 and 30 but were released only recently by the US government's Defence Visual Information Distribution Service (DVIDS).

"The PLAN task force includes a guided-missile cruiser, a guided-missile destroyer, a general intelligence vessel, and an auxiliary vessel," according to the original caption given by DVIDS, according to The Drive.

China's state-owned media reported that the four ships were likely part of a flotilla that passed east from the Soya Strait on August 24, putting them on a course that would have brought them close to Alaska. The Japan Maritime Self-Defence Force identified the four ships like the "Type 055 destroyer Nanchang, the Type 052D destroyer Guiyang, a Type 903A supply ship with hull number 903, and a surveillance ship with hull number 799."

Type 055 is classified as a 'cruiser' by the US Navy. The Type 055 class of ships is China's most advanced surface warship to date, with a sophisticated radar system capable of engaging multiple targets in the air.

In September 2015, the Chinese People's Liberation Army Navy (PLAN) made a similar passage off the coast of Alaska.

Five warships were involved in the passage at the time, which the US called an "innocent passage" because it passed within 12 nautical miles of the Aleutian Islands.