The United States and Canada offered words of encouragement to the tens of thousands of pro-democracy protesters whom police tried to disperse with blasts of tear gas and pepper spray.
The street clashes in the global financial capital came up at Monday's White House press briefing, where a spokesman for President Barack Obama said the U.S. was watching the situation closely.
"The United States supports universal suffrage in Hong Kong in accordance with the Basic Law (of 1990), and we support the aspirations of the Hong Kong people," said White House press secretary Josh Earnest.
"We believe that an open society with the highest possible degree of autonomy and governed by the rule of law is essential for Hong Kong’s stability and prosperity. Indeed, this is what has made Hong Kong such a successful and truly global city to this point."
He was asked whether he hoped those aspirations might spread to mainland China and replied: "The short answer to that is yes."
In Ottawa, a spokesman for Foreign Affairs Minister John Baird said Canada was concerned and was monitoring developments closely. Adam Hodge said Canada supported democratic development in Hong Kong under a "One Country, Two Systems" policy that had contributed to the region's stability and prosperity.
China has managed to block most images of the protests from popular websites, shut down social-media sites, and has had relatively little news coverage of the events in its state-controlled media.
On Monday afternoon, the front page of the Xinhua news English-language site contained a story about an anti-government protest — in Pakistan. It also had a story about one country's clampdown on a vote in one of its autonomy-seeking regions. That country was Spain, and the region was Catalan.
But there wasn't any mention of the huge crowds in Hong Kong. There was one piece on the Mandarin-language version of the site that described an illegal street occupation that was trying to paralyze Hong Kong and blackmail the central and regional governments.
Demonstrators are challenging Beijing's plan to reject open nominations in the first-ever elections for Hong Kong's leader, promised for 2017. Beijing intends to approve the candidates — which protesters consider a violation of the 1990 Basic Law, drafted before the former British colony reverted to Chinese rule.
The Chinese government delivered a blunt message to outsiders during a press conference Monday.
"I'd like to reiterate that Hong Kong is China's Kong Kong, which is a special administrative region of China," Foreign Ministry spokesperson Hua Chunyin said, according to a government-issued transcript.
"We hope that relevant countries can be prudent in their words and deeds, refrain from interfering in the internal affairs of Hong Kong in any way, stay away from supporting the illegal acts such as 'Occupy Central,' and do not send out wrong signals."
A petition on the White House website urging support for the protests quickly smashed the 100,000-signature threshold that requires a response from the Obama administration.
But the U.S. government was forced to confront its own recent track record in dealing with street protests. The Chinese media had offered extensive coverage a few weeks ago of the scenes in Ferguson, Mo., as protesters and journalists were arrested following the shooting of an unarmed black teenager by police.
One reporter asked Earnest how the clampdown in Hong Kong differed from the one in Ferguson.
The president's press secretary replied that the response from each national government could hardly have been more different. He noted that the U.S. government intervened to allow free expression in Ferguson.
The president even made a point of referring to Ferguson in his speech last week to the United Nations General Assembly, he noted.
"No country is perfect. Our country is not perfect," Earnest said.
"But what we are seeking to do is to form a more perfect union. And when we strive to address those differences, we do so in the open light of day, in the open light of our democracy."