Thousands of Hong Kong residents have queued up outside the city's British consulate this week to sign a condolence book for the late monarch who died after 70 years on the throne.

Among the mourners was Law Kar-ying, a heavyweight of the Cantonese opera scene, who published a selfie on Instagram from the queue and a message that read: "Hong Kong was a blessed land during her reign."

Instagram is banned in mainland China, but Law's post went viral on other social media sites, sparking anger and criticism among nationalists.

On Thursday, Law took to China's Twitter-like platform Weibo to post a video apologizing for "making remarks of mourning without thinking them through".

"My original intention was to express condolences for a late elderly woman, and I would like to appeal to everyone not to overly interpret what I said," the 75-year-old said in Mandarin Chinese.

"I can't possibly forget my origin and ancestry. That I have been keeping a Chinese passport says it all, I am Chinese, and I love my motherland forever. I am sorry," he added.

His original Instagram post was deleted.

Hong Kong was a British colony for over 150 years and while the financial hub was returned to China in 1997, the past is engraved into its landscape, from street names and the ubiquity of English to the common law legal system.

While other former colonies have seen more muted reactions to Elizabeth II's death, about 6,700 Hong Kong residents, including some government officials, have signed the consulate's condolence book so far.

Queues have snaked through the business district and taken up to four hours.

Many mourners have expressed nostalgia for the city's colonial past at a time when China is seeking to purge dissent following huge democracy protests three years ago.

Ta Kung Pao, a Hong Kong newspaper which answers to Beijing's local Liaison Office, ran a commentary on Tuesday accusing "anti-Chinese elements and anti-China media" of "whitewashing colonial rule" by encouraging mourning of Elizabeth II.

Nationalism has surged under President Xi Jinping, China's most assertive and authoritarian leader in a generation.

Celebrities and businesses can find themselves facing huge consumer backlashes for any perceived slight to China or suggestion of disloyalty.

Many of the commenters underneath Law's Weibo video were not convinced by his apology.

Some told him to "learn from his wife" Liza Wang, a veteran actress who was a Hong Kong delegate to China's top political advisory body for two decades.