Facebook co-founder and CEO Mark Zuckerberg has started his visit to China with a tour of the offices of the country's top search engine, while his own social networking site remains blocked on the mainland.

Photos of Zuckerberg's visit to Baidu Inc. on Monday morning were posted online.

Baidu's director of international communications said he wasn't going to deny what was in the photos. Kaiser Kuo said Zuckerberg was meeting with Baidu CEO Robin Li, but he didn't know what they were discussing.

Kuo said not many in China are familiar with Facebook, but that Zuckerberg is known for being Time magazine's 2010 Person of the Year.

Zuckerberg is traveling with his girlfriend and no apparent entourage. His China schedule is not known.