Facebook CEO Mark Zuckerberg on Thursday announced that two top executives are leaving the company.

Chris Cox, Facebook's top executive in charge of products, and Chris Daniels, the head of messaging service WhatsApp, will be departing for unspecified reasons, according to a blog post from Zuckerberg.

Cox, a Facebook veteran who has been a close adviser to Zuckerberg for years, decided to leave his role months after he was promoted to oversee all of the company's apps, including Instagram, WhatsApp and Facebook Messenger.

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"It is with great sadness I share with you that after thirteen years, I’ve decided to leave the company," Cox wrote in a Facebook post.

Zuckerberg did not say why Daniels is leaving, but noted that he will be replaced by Will Cathcart, a vice president of product management who has been running the Facebook app.

The high-level departures come shortly after Zuckerberg announced that Facebook will be reorienting itself to become a more privacy-minded platform.

Cox wrote that Facebook will "need leaders who are excited to see the new direction through."

"As Mark has outlined, we are turning a new page in our product direction, focused on an encrypted, interoperable, messaging network," Cox wrote. "It's a product vision attuned to the subject matter of today: a modern communications platform that balances expression, safety, security, and privacy."

The company's proposed "privacy-first" approach marks a radical shift in Facebook's mission, reorienting from a focus on the platform's public-facing News Feed feature — which Cox helped create — to its private messaging services.

The plan involves integrating Instagram Direct, WhatsApp and Facebook Messenger, allowing users to communicate across the different platforms.

Current and former employees told The New York Times that the decision to integrate the messaging services has caused some controversy and rifts internally.

Facebook over the last two years has faced an ongoing barrage of scandals over its data privacy practices, which the company has been forced to explain and offer apologies for.

Zuckerberg in his post wrote that Cox was planning to leave several years ago, but he stayed in order to address the issues that emerged in 2016.

The 2016 presidential election marked a significant shift in public perception of Facebook, as critics said the platform was used to manipulate public opinion and sow discord during a pivotal election year.

The controversy boiled over following revelations that political consultancy firm Cambridge Analytica improperly obtained data on 87 million users.

"For a few years, Chris has been discussing with me his desire to do something else," Zuckerberg wrote. "He is one of the most talented people I know and he has the potential to do anything he wants."

"As we embark on this next major chapter, Chris has decided now is the time to step back," Zuckerberg wrote.

The departures also come as Facebook faces investigations by the Justice Department's securities fraud division, the Federal Trade Commission (FTC) and the Securities and Exchange Commission.

--Updated at 5:03 p.m.