Chinese aircraft carrier the Liaoning entered Taiwan's air defence identification zone early on Wednesday morning on its way back from Hong Kong and is being monitored, Taiwan's defence ministry said, adding there was no cause for alarm.

The Liaoning left Hong Kong at noon on Tuesday, before entering Taiwan's defence zone by travelling in a northerly direction via the western side of the Taiwan Strait, the ministry said.

Taiwan was monitoring the situation, had detected nothing unusual and people should not be alarmed, it added.

The Soviet-built Liaoning, China's first aircraft carrier, had been in Hong Kong for events marking the 20th anniversary of the territory's return to Chinese rule from Britain.

It was the fourth time that the Liaoning has sailed near self-ruled Taiwan, which China claims as its own, in recent months for what Beijing has said were routine drills.

Earlier this month Taiwan scrambled jets to shadow the carrier as it made its way to Hong Kong.

China has never renounced the use of force to bring Taiwan, which China considers a wayward province, under its control.