When asked whether the military will step in, China's Defense 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.
Xinhua showed pictures of armoured personnel carriers and trucks carrying troops at the border, though it was unclear from the caption if they were passing into or out of Hong Kong.
The well-publicised troop movement comes days before a planned new mass rally on Saturday which was expected to draw hundreds of thousands to the Hong Kong's streets.
G7 leaders meeting in France on Monday backed Hong Kong's autonomy as laid out in a 1984 agreement between Britain and China, and called for calm in the protest-hit city.
It has since evolved into calls for greater democracy under the "one country, two systems" formula enshrined in the Basic Law under which Hong Kong has been administered since the return from British to Chinese rule.
Sy, who says she was given no reason for her dismissal, said her firing sends a clear message to the people in Hong Kong that it's not about whether you broke the law but simply whether you are doing what you have been told to do.
However, demands of demonstrators have grown and the protests themselves have become more violent, prompting officials in Beijing to issue stark warnings of a possible crackdown.
Beijing is eager to quell the unrest before the 70th anniversary of the founding of the People's Republic of China on October 1, when Xi will oversee a large military parade in the Chinese capital.
Meanwhile Selina, a Mainland Chinese student studying for a master's degree in communication and working for a local media company, said that what makes her feel more angry and disappointed was "unscrupulous media and some Hong Kong people that were just watching the drama" of the violent protests.
Both business and leisure travel into Hong Kong has "weakened substantially" and traffic from the city has started to soften, especially on short-haul routes to China and South Korea, Cathay said.
"That is why local government on Tuesday said it is confident to tackle the ongoing protest by legal means", said Chien-Yu Shih, a Taiwanese scholar who teaches at Hong Kong Chuhai College. While China is already threatening action on Taiwan due to its support for Hong Kong protests, the implications might be far worse.
Hong Kong International Airport was forced to close earlier this month after protesters demonstrated in the arrival building and fought with police.
The protest would mark five years since Beijing ruled out universal suffrage for Hong Kong.