Reuters reporters in China were unable to send messages on Line, owned by South Korea's Naver Corp, and KakaoTalk, owned by South Korean firm Kakao Corp. Both companies told Reuters they did not know the cause of the disruption or when the services would return to normal.
Microsoft declined to give immediate comment. Yahoo was unavailable for immediate comment.
"This is not a technical malfunction," said a member of China-based anti-censorship site GreatFire.org, who goes by the pseudonym of Charlie Smith."I imagine these latest blocks are attributable to the Hong Kong demonstrations," Smith said, adding that the services may have been blocked because they can be used for photo sharing.
On Tuesday, thousands of pro-democracy protesters marched in Hong Kong in one of the biggest challenges to China's Communist Party rule in more than a decade.
Some users of Chinese microblog Weibo Corp who commented on the march said on social media that their accounts had been blocked or removed.
Chinese authorities with oversight of the Internet were not immediately available for comment.
Line said that it already cooperates with China's government to censor banned phrases. "In order for Line to advance into China, there was the need to adapt to the local environment," a company spokeswoman said.
Since President Xi Jinping took power last year, the government has throttled online dissent and harshly punished those it views as critics of Communist Party rule and threats to its stability. Campaigns to 'clean the Internet' and get rid of rumour mongering and pornographic material have affected both domestic and overseas Internet services.
The Google disruption began in the run-up to the 25th anniversary of government's bloody crackdown on pro-democracy demonstrators around Beijing's Tiananmen Square.
© Thomson Reuters 2014