US tech giants Facebook Inc, Alphabet Inc's Google and Twitter Inc have privately warned the Hong Kong government that they could stop offering their services in the city if authorities proceed with planned changes to data-protection laws, the Wall Street Journal reported on Monday, citing a letter.

The laws could make the tech companies liable for the malicious sharing of individuals' information online, the newspaper added.

A letter sent by an industry group that includes the internet firms said companies are concerned that the planned rules to address "doxing" could put their staff at risk of criminal investigations or prosecutions related to what the firms' users post online, Journal reported.

Doxing is an act of revealing people's personal information such as real name, home address or workplace online without the user's permission.

Facebook, Google and Twitter did not immediately respond to Reuters' requests for a comment.

Hong Kong's Constitutional and Mainland Affairs Bureau in May proposed amendments to the city's data-protection laws that it said were needed to combat doxing, a practice that was prevalent during 2019 protests in the city, the newspaper said.

According to the newspaper, the letter dated June 25 was sent by Singapore-based Asia Internet Coalition.

"The only way to avoid these sanctions for technology companies would be to refrain from investing and offering the services in Hong Kong," the Journal reported, quoting the letter.