HONG KONG: China's military deployed fresh troops to Hong Kong early Thursday in what it called a routine rotation amid speculation that it might intervene in the city's pro-democracy protests.

Footage on CCTV showed armoured carriers, trucks and a patrol boat crossing the border at night from the neighbouring city of Shenzhen. Scores of soldiers ran in unison onto trucks, which the state broadcaster said were bound for various ports and entry points into Hong Kong. A handover ceremony was held overnight.

"This time the task has a glorious mission. The responsibility is great. The job is difficult," a major said to troops before they departed. "The time for a true test has arrived!"

The official Xinhua News Agency said it was the 22nd rotation of the People's Liberation Army's garrison in Hong Kong. The previous one was in August 2018.

Nearly three months of fiery anti-government demonstrations have sparked concerns that the military will be deployed in the semi-autonomous Chinese city. The Hong Kong garrison previously published a promotional video with scenes of soldiers facing off with people dressed like protesters.

The soldiers in the new rotation were educated on Hong Kong's laws and vowed to defend the nation's sovereignty, Xinhua said.

"We will firmly follow the command of (the ruling Communist Party)," Liu Zhaohui, the garrison's deputy chief of staff, said on CCTV. "We will firmly implement the guideline of 'one country, two systems' and the Basic Law and the Garrison Law of Hong Kong."

A former British colony, Hong Kong was returned to China in 1997 under the "one country, two systems" framework, which promises the city certain democratic rights that are not afforded to the mainland. In recent years, however, some Hong Kong residents have accused Beijing of steadily eroding their freedoms.

When asked whether the military will step in, China's Defence Ministry has pointed to a provision in the Garrison Law which allows Hong Kong-stationed troops to help maintain public order at the request of the city government. Hong Kong authorities, however, have said they can handle the situation themselves.

Troops stationed in Macao, another special administrative region, also completed a rotation Thursday.

The last rotation of the Hong Kong garrison occurred one year prior. The Xinhua report on that rotation in August 2018 does not mention "one country, two systems" or national sovereignty.