Staff departures in recent days include dozens of people spread across units such as government policy, legal affairs and Twitter’s “trust and safety” division, which is responsible for functions like drafting content-moderation rules, according to current and former employees, postings on social media and emails sent to work addresses of people who had worked at Twitter that recently bounced back. They have left from hubs including Dublin, Singapore and San Francisco.

Many of the departures follow Mr. Musk’s ultimatum late last week that staffers pledge to work long hours and be “extremely hardcore” or take a buyout. Hundreds or more employees declined to commit to what Mr. Musk has called Twitter 2.0 and were locked out of company systems. That comes after layoffs in early November that cut roughly half of the company’s staff.

Twitter conducted another round of job cuts affecting engineers late Wednesday, before the Thanksgiving holiday in the U.S., people familiar with the matter said. The exact scope couldn’t be immediately learned, though some of the people estimated dozens of employees were let go.

Twitter sent fired engineers an email saying their code wasn’t satisfactory and offering four weeks of severance, some of the people said. Some other engineers received an email warning them to improve their performance to keep their jobs, the people said.

Ireland’s Data Protection Commission said this week it was asking Twitter whether it still had sufficient staff to assure compliance with the European Union’s privacy law, the General Data Protection Regulation, or GDPR. The company last week told the Irish data regulator that it did, but is still reviewing the impact of the staff departures, a spokesman for the Irish regulator said.

He said Twitter has appointed an interim chief data protection officer, an obligation under the GDPR, after the departure of Damien Kieran, who had served in the role but left shortly after the first round of layoffs.

In France, meanwhile, the country’s communications regulator said it sent a letter last Friday asking that Twitter explain by this week whether it has sufficient personnel on staff to moderate hate speech deemed illegal under French law—under which Twitter could face legal orders and fines.

The staff departures come as Twitter holds talks with the EU about the bloc’s new social-media law, dubbed the Digital Services Act, which will apply tougher rules on bigger platforms like Twitter by the middle of next year.

Didier Reynders,

the EU’s justice commissioner, is slated to attend a previously scheduled meeting with Twitter executives in Ireland on Thursday. He plans to ask about the company’s ability to comply with the law and to meet its commitments on data protection and tackling online hate speech, according to an EU official familiar with the trip.

Věra Jourová, a vice president of the EU’s executive arm, said she was concerned about reports of the firing of vast amounts of Twitter staff in Europe. “European laws continue to apply to Twitter, regardless of who is the owner,” she said.

Mr. Musk has said that he would follow the laws of the countries where Twitter operates and that it “cannot become a free-for-all hellscape.”

Twitter didn’t respond to a request for comment.

Late Wednesday, Mr. Musk tweeted that the number of views of tweets he described as “hate speech” had fallen below levels seen before a spike in such views in late October.
“Congrats to the Twitter team!” Mr. Musk wrote. 

Some of the people who either departed or declined to sign on to Twitter 2.0 appear to include Sinead McSweeney, the company’s Ireland-based vice president of global policy and philanthropy, who led government relations and compliance initiatives with regulations worldwide, as well as the two remaining staffers in Twitter’s Brussels office.

Ms. McSweeney and the two Brussels employees declined to comment, but emails to their work addresses started bouncing back undeliverable in recent days according to checks by The Wall Street Journal. Four other Brussels-based employees were earlier this month told they were being laid off, according to social-media posts and people familiar with the matter.

Damien Viel, Twitter’s country manager for France, was also among a wave of staffers who posted publicly this week that they had left the company. He declined to comment when reached by the Journal.

At least some of the departures occurred in teams that reported to

Yoel Roth,

Twitter’s former head of trust and safety, who resigned earlier this month. In an op-ed for the New York Times, Mr. Roth said he resigned because Mr. Musk made it clear that he alone would make decisions on policy and the platform’s rules and that he had little use for those at the company who were advising him on those issues.

The team included Ilana Rosenzweig, who worked as Twitter’s senior director and head of international trust and safety. She has left the company, according to her LinkedIn profile. Based in Singapore, Ms. Rosenzweig led Twitter’s trust and safety teams across Europe, the Middle East and Africa, along with Japan and other Asia-Pacific countries, according to her profile.

“I decided not to agree to Twitter 2.0,” Keith Yet, a Twitter trust and safety worker based in Singapore, wrote on LinkedIn on Monday. Mr. Yet worked on child sexual exploitation issues and handling legal escalations from Japan and other countries, according to his LinkedIn profile. Attempts to reach Ms. Rosenzweig and Mr. Yet were unsuccessful.

The departures come amid a wave of new tech regulation, particularly in Europe. The Digital Services Act, which will by the middle of next year require tech companies like Twitter with more than 45 million users in the EU to maintain robust systems for removing content that European national governments deem to be illegal. 

The act also requires these companies to reduce risks associated with content that regulators consider harmful or hateful. It mandates regular outside audits of the companies’ processes and threatens noncompliance fines of up to 6% of a company’s annual revenue.

Political leaders had warned that Mr. Musk’s Twitter would have to comply with EU rules. “In Europe, the bird will fly by our rules,” tweeted the EU’s commissioner for the internal market,

Thierry Breton,

hours after Mr. Musk completed his Twitter deal in late October tweeting, “the bird is free.”

A spokesman for the European Commission, the EU’s executive arm, said this week that it had active contacts with the company regarding the regulation and tackling disinformation and illegal hate speech, but declined to comment on the substance of Twitter’s compliance plans.

Activists and researchers are also concerned that the departures could undermine Twitter’s ability to block state-backed information operations aimed at spreading propaganda and harassing adversaries. The wave of departures “raises questions about how Twitter will moderate tweets and comments in a professional and neutral manner,” said Patrick Poon, an activist turned scholar at Japan’s Meiji University, who analyzes free speech.

—Liza Lin, Alexa Corse and Sarah E. Needleman contributed to this article.

Write to Sam Schechner at Sam.Schechner@wsj.com, Kim Mackrael at kim.mackrael@wsj.com and Newley Purnell at newley.purnell@wsj.com