Flickr.com, one of the world's most popular online photo-sharing sites and owned by Yahoo Inc., is likely being blocked by the Chinese government, Yahoo's Hong Kong unit said on Tuesday.

Flickr -- popular among a growing class of digital photo enthusiasts in the world's second-largest Internet market -- has not shown photos to users in mainland China since last week, amid rumors Beijing took action after images of the Tiananmen massacre in early June 1989 were posted.

It is our understanding that Flickr users in China are not able to see images on Flickr, and we have confirmed that this is not a technical issue on our end, a spokeswoman for Yahoo Hong Kong said in an email in response to a Reuters inquiry.

It appears that the Chinese government is restricting access to Flickr, although we have not received confirmation from them, the spokeswoman said in the email.

We are currently investigating this issue and hope that it is only a temporary one, she added.

Officials from China's Ministry of Information Industry could not be reached for comment on Tuesday.

The Communist Party has banned references to the June 4, 1989 Tiananmen Square crackdown in state media, the Internet and books as part of a whitewash campaign, meaning most young Chinese are ignorant of the events.

Public discussion of the massacre is still taboo in China and the government has rejected calls to overturn the verdict that the student-led protests were subversive. Hundreds, perhaps thousands, were killed when the army crushed the democracy movement.

A newspaper in southwest China sacked three of its editors over an advertisement saluting mothers of protesters killed in the crackdown, sources told Reuters last week.

Yahoo is also no stranger to challenges while operating in China, which has over 140 million Web users.

Press watchdogs accused Yahoo Holdings (Hong Kong) Ltd. two years ago of providing details about e-mail communications that helped identify, and were used as evidence against, Shi Tao, who was sentenced to 10 years in prison for leaking state secrets abroad.

Yahoo Inc. defended itself at the time by saying it had to abide by local Chinese laws.

Flickr also said on Monday it is moving to further internationalize its service by creating versions in seven major languages besides English, including Chinese.

Yahoo China -- which was absorbed by e-commerce company Alibaba in 2005 -- had a nine percent share of China's online photo-sharing market last year, according to IT consultancy iResearch.

Online services such as Flickr, Shutterfly Inc., Eastman Kodak's EasyShare Gallery and Hewlett-Packard Co.'s Snapfish let users load digital pictures online, where they can be edited, shared with others, printed and mailed.

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