Enlarge Image James Martin/CNET

Donald Trump may be a Facebook fan, but it's a pretty good guess that he's not liking Mark Zuckerberg's most recent posts.

Facebook's CEO kicked off the company's F8 developer conference Tuesday with a thinly veiled shot at the front-runner for the Republican Party's presidential nomination. He followed that with a post on his social network, saying that his presentation was different from "any other speech I've given."

"I hear fearful voices calling for building walls and distancing people they label as others," Zuckerberg told more than 2,000 people in San Francisco attending F8. "If the world starts to turn inwards, then our community will just have to work even harder to bring people together."

The Trump campaign wasn't amused.

"I'll take Mark Zuckerberg seriously when he gives up all of his private security -- move out of his posh neighborhood and come live in a modest neighborhood near a border town," Trump spokeswoman Katrina Pierson told CNBC. "Then I'm sure his attitude would change."

The dustup between the two billionaires comes as Zuckerberg, 31, has been playing a more hands-on role on the world stage. In the past year, he's met with world leaders including President Barack Obama, Indian Prime Minister Narendra Modi and Chinese President Xi Jinping. He's also spoken out on social issues such as vaccines and terrorism.

Zuckerberg has indirectly criticized Trump before, saying he didn't agree with the candidate's anti-Muslim rhetoric. But in his follow-up post to Tuesday's remarks, Zuckerberg said he wasn't talking about one person or one country. He just wanted to share his hope for connecting people around the world. "It's about having the courage to choose hope over fear," he wrote.

Trump's campaign fired back anyway, saying "self-righteousness isn't very productive."

"We can talk about taxes, we can talk about jobs and even immigration, but that doesn't really put food on the table and save lives," Pierson said.

The Trump campaign didn't respond to a request for further comment. A Facebook spokeswoman declined to comment beyond Zuckerberg's speech and post.