It cited one of the soldiers as saying that their action has nothing to do with the Hong Kong government.
"We volunteered! Stopping the violence and ending chaos is our responsibility," the soldier was quoted as saying.
However, their action was condemned by the Opposition lawmakers for breaching the Basic law and the Garrison Law.
According to SCMP, the laws state that the garrison "shall not interfere in local affairs" and must tell the Hong Kong government in advance for "military activities such as training or manoeuvres involving public interests".
A government spokesperson for the city government was quoted as saying that the garrison had volunteered its services and it was not at their request. A PLA spokesman said, "some soldiers saw that local residents were cleaning the road outside the barracks and decided to help."
On its Weibo account, PLA described it as "a voluntary act to help local residents and to clear up roads around the barracks".
This comes amidst rising speculations if the mainland would use PLA to crush the protests that have rocked Hong Kong.
The Chinese President Xi Jinping had recently said that the most pressing task for Hong Kong at present is to bring violence and chaos to an end and restore order.
On November 15, it was reported that anti-government protestors in Hong Kong continued their blockade of parts of the city for the fifth consecutive day on Friday, forcing schools to shut and blocking highways.