Japan's defence minister said on Tuesday the appearance of the Chinese aircraft carriers signified Beijing's intention to further widen its capabilities beyond its borders.
Taiwan's Defence Minister Wellington Koo said the armed forces had a "full grasp" of the carriers' movements.
"Crossing from the first island chain into the second island chain sends a definite political message and their expansionist nature can be seen," he told reporters in Taipei on Wednesday.
The first island chain refers to an area that runs from Japan down to Taiwan, the Philippines and Borneo, while the second island chain spreads further out into the Pacific to include places like the US territory of Guam.
China's navy, which has been honing its abilities to operate further and further from the country's coast, said on Tuesday the carrier operations were a "routine training" exercise that did not target specific countries or regions.
Taiwan, which China views as its own territory, keeps a close watch on Chinese military movements given the regular drills and war games Beijing stages around the island.
Since May, China has been flexing its muscles by sending an unusually large number of naval and coast guard vessels through a swathe of East Asian waters, according to security documents and officials, in moves that have unnerved regional capitals.
Japan's defence ministry confirmed the two carriers, Liaoning and Shandong, were operating in separate areas in the Pacific on Saturday, both near remote southern islands belonging to Japan.
Earlier, Japan said the Liaoning sailed within its exclusive economic zone near Minamitorishima, a remote island east of Iwo Jima.
