People walk outside Twitter headquarters in San Francisco, Nov 4, 2022 as employees braced for widespread layoffs at Twitter with new owner Elon Musk overhauling the social platform. (JEFF CHIU / AP)

Twitter Inc laid off half its workforce on Friday but said cuts were smaller in the team responsible for preventing the spread of misinformation, as advertisers pulled spending amid concerns about content moderation.

Tweets by staff of the social media company said teams responsible for communications, content curation, human rights and machine learning ethics were among those gutted, as were some product and engineering teams.

The move caps a week of chaos and uncertainty about the company's future under new owner Elon Musk, the world's richest person, who tweeted on Friday that the service was experiencing a "massive drop in revenue" from the advertiser retreat.

READ MORE: Twitter temporarily closes offices as layoffs begin

Musk blamed the losses on a coalition of civil rights groups that has been pressing Twitter's top advertisers to take action if he did not protect content moderation – concerns heightened ahead of potential pivotal congressional elections on Tuesday.

Unfortunately there is no choice when the company is losing over $4M/day.

Elon Musk, Owner, Twitter

After the layoffs, the groups said they were escalating their pressure and demanding brands pull their Twitter ads globally.

"Unfortunately there is no choice when the company is losing over $4M/day," Musk tweeted of the layoffs, adding that everyone affected was offered three months of severance pay.

The company was silent about the depth of the cuts until late in the day, when head of safety and integrity Yoel Roth tweeted confirmation of internal plans, seen by Reuters earlier in the week, projecting the layoffs would affect about 3,700 people, or 50 percent of the staff.

Among those let go were 784 employees from the company's San Francisco headquarters and 199 in San Jose and Los Angeles, according to filings to California's employment authority.

Roth said the reductions hit about 15 percent of his team, which is responsible for preventing the spread of misinformation and other harmful content, and that the company's "core moderation capabilities" remained in place.

Musk endorsed the safety executive last week, citing his "high integrity" after Roth was called out over tweets critical of former President Donald Trump years earlier.

Musk has promised to restore free speech while preventing Twitter from descending into a "hellscape."

Elon Musk arrives at Baron Investment Conference at the Metropolitan Opera House, Nov 4, 2022, in New York. Musk tweeted on Friday that Twitter Inc was experiencing a "massive drop in revenue" from the advertiser retreat. (YUKI IWAMURA / AP)

President Joe Biden said on Friday that Musk had purchased a social media platform in Twitter that spews lies across the world.

"And now what are we all worried about: Elon Musk goes out and buys an outfit that sends – that spews lies all across the world… There’s no editors anymore in America. There’s no editors. How do we expect kids to be able to understand what is at stake?"

Major advertisers have expressed apprehension about Musk's takeover for months.

ALSO READ: Advertisers begin to grill Musk over Twitter 'free-for-all'

Brands including General Motors Co and General Mills Inc have said they stopped advertising on Twitter while awaiting information about the new direction of the platform.

Musk tweeted that his team had made no changes to content moderation and done "everything we could" to appease the groups. Speaking at an investors conference in New York on Friday, Musk called the activist pressure "an attack on the First Amendment."

Twitter did not respond to a request for comment.