TikTok users inundated congressional offices with calls Thursday after the company sent pop-up messages urging people to “speak up” against a rapidly moving House proposal that could lead to the China-linked app being banned in the United States.

The app displayed messages asking people to contact their representatives to “stop a TikTok shutdown” ahead of a key committee vote on the bill, a tactic that triggered a flood of calls to offices on Capitol Hill — many in protest.

Individual House offices have since received hundreds of calls from TikTok users, at times fielding upward of 20 a minute, according to eight congressional aides, who spoke on the condition of anonymity to describe the outreach. The volume has been so immense that some offices resorted to temporarily shutting off phones, two aides said, while others struggled to field unrelated calls.

The episode began just hours before lawmakers advanced a bill explicitly targeting TikTok and other apps they accuse of being “controlled” by foreign adversaries, such as China. The proposal could force TikTok’s China-based parent company to sell off the app or block it entirely in the United States. The legislation sailed out of the House Energy and Commerce Committee unopposed Thursday afternoon, 50-0, in a sweeping bipartisan rebuke of the app.

The proposal is the latest in a long series of bills that seek to give the federal government more power to boot out apps from the United States that it deems a security threat — with some expressly naming TikTok. But those measures have faced pushback from civil liberties groups, which say they are unconstitutional and would infringe on millions of users’ rights to free expression online.

TikTok officials have said repeatedly that the company is not influenced by the Chinese government and that its owner, China-based ByteDance, is 60 percent owned by international investors.

Rep. Raja Krishnamoorthi (D-Ill.), who backed the legislation, said Thursday in a post on X that the effort was a “massive propaganda campaign.”

On Thursday, some users who opened the app were shown a full-screen message: “Let Congress know what TikTok means to you and tell them to vote NO,” the screen read, above a red “Call Now” button.

A pop-up asked users for their Zip code, spitting out their local congressional district and representative. TikTok, like other social media apps, collects information on users’ rough locations via their IP addresses but does not use more precise GPS data.

The app also sent users a push notification saying, “TikTok is at risk of being shut down in the US. Call your representative now.”

Some congressional aides said the callers bombarding their offices skewed young, while others said they appeared to range in age from teens to senior citizens.

TikTok spokesman Alex Haurek told The Washington Post that the prompt was sent only to voting-age users who are 18 or older. The screen did not force users to call their congresspeople, he said, and it could be easily closed, via an “X” button, or swiped away.

Haurek declined to say how many users had been shown the pop-up but said it was being sent across the United States and was not being targeted to any specific location or congressional district.

Rep. Mike Gallagher (R-Wis.), who introduced the measure with Krishnamoorthi, said the pop-up was an “example of an adversary-controlled application lying to the American people and interfering with the legislative process in Congress.”

Haurek accused the committee on Thursday of passing legislation with “a predetermined outcome: a total ban of TikTok in the United States.”

During the markup session, lawmakers pushed back on that assertion, with Rep. Anna G. Eshoo (D-Calif.) saying she supported the app divesting from ByteDance but opposed a total ban. Before the session, however, some committee members said they hoped the proposal would lead to just that.

“No one is trying to disguise anything. You’re correct — we want to ban TikTok,” Rep. Dan Crenshaw (R-Tex.) posted in response to a message from TikTok.

TikTok has faced existential threats in Washington since 2020, when then-President Donald Trump called for the app to be banned or forced to be sold. That effort was overruled by federal judges, who said the government had not provided proof that the app’s national-security risks outweigh Americans’ rights to free expression.

The Biden administration pushed ByteDance last year again to divest and lent its support to a congressional measure called the Restrict Act that could lead to the app’s ban. But that legislation stalled under criticism, including from Republicans such as Sen. Rand Paul, who said it represented a government overreach.

Some states have moved to ban TikTok on university campuses and state-owned devices. Montana’s statewide ban, however, was blocked late last year by a federal judge, who said it “violates the Constitution in more ways than one.”

The Committee on Foreign Investment in the United States, an interagency group that reviews business transactions for national security threats, has been negotiating with the company for years. The company has proposed a $1.5 billion corporate-reform plan, Project Texas, that it says would address all of the government’s privacy and data-security concerns, but CFIUS has yet to approve the plan.

As efforts within the executive branch to confront the app have faltered, lawmakers on Capitol Hill have stepped in with a flurry of bills taking aim at TikTok and similarly situated platforms, including a Senate-led effort to give the Commerce Department more leeway to restrict them.

Thursday’s committee vote marks one of the most significant legislative threats to the platform to date — and it’s quickly gaining steam.

The committee marked up and advanced the measure unanimously just two days after it was introduced, a rare breakneck pace that could fast-track its trajectory to the House floor. House Speaker Mike Johnson (R-La.) and the White House have voiced support for the efforts this week, as have other key House committee leaders. House Majority Leader Steve Scalise (R-La.) announced he planned to bring the bill to a floor vote next week.

Rep. Frank Pallone Jr. (N.J.), the committee’s top Democrat, said during the markup that it was not “necessary to rush this process” but later voted to advance the bill.

It’s unclear how much traction the push will gain in the Senate, where lawmakers have proposed competing bills to address their concerns over TikTok.

The American Civil Liberties Union, the Electronic Frontier Foundation, the Center for Democracy and Technology and other advocacy groups have voiced opposition to the bill, the Protecting Americans from Foreign Adversary Controlled Applications Act.

“Congress can protect data privacy and security without banning Americans from accessing one of the world’s most popular communications platforms,” Jameel Jaffer, executive director of the Knight First Amendment Institute at Columbia University, said in a statement Tuesday.

TikTok has demonstrated an outsize ability for political mobilization. In 2020, TikTokers flooded the ticket-booking website for a Trump campaign rally in Tulsa, and some users rejoiced when the event, which Trump’s campaign manager said had received a million ticket requests, garnered fewer than 6,500 attendees.

The federal government, which bans TikTok on government-owned devices, has also worked to benefit from that mass influence. President Biden’s reelection campaign officially joined TikTok last month, and the White House held briefings today for dozens of TikTok creators ahead of Biden’s State of the Union address.

TikTok is not the first tech company to try to flex its technology for political outcomes. In 2014, the ride-sharing app Uber, then facing resistance from government transportation agencies, sent a notification to users in Virginia that called on them to demand changes — and even included the phone number and email address of a local official who’d pushed to halt the firm’s operations.

In 2020, Uber and a similar app, Lyft, sent notifications to California users encouraging them to vote yes on Proposition 22, a ballot measure that would allow the companies to continue classifying their drivers as contractors instead of employees. The measure won with 58 percent of the vote.

TikTok’s messaging is “equally aggressive,” said Bradley Tusk, an early Uber investor and adviser who helped craft these campaigns for the ride-hailing company. But because of its ties overseas, Tusk said, “TikTok has a much harder road ahead.”

Nitasha Tiku contributed to this report.