London (CNN Business) Protests are taking place at Google offices Wednesday, following allegations of retaliation from the company against employees who participated in walkouts last year.

Leaders of the protests have called on their co-workers to participate in sit-ins at Google offices around the world, six months after walkouts over the company's handling of sexual harassment claims

Organizers publicized the protests on Twitter , and oneemployee told CNN Business that workers from at least 15 offices in the United States were expected to participate. A second employee in London confirmed that protests were planned for Wednesday.

Thousands of Google employees walked out in November after a New York Times report detailed years of sexual harassment allegations at the company and big payouts for accused executives.

Google made some changes to its internal policies following the protests,including eliminating its forced arbitration policies for employees bringing sexual assault or harassment claims.

But protest organizers say that some workers who participated in the walkouts or voiced concerns about sexual harassment and discrimination have faced retaliation from Google.

According to Wired , at least two employees involved with organizing the walkouts have accused the company of retaliation following the walkout. One claims she was demoted, while a second says her job was restructured.

"From being told to go on sick leave when you're not sick, to having your reports taken away, we're sick of retaliation," organizers tweeted Tuesday from the Twitter account @GoogleWalkout.

Today, Googlers from around the world are gathering at 11am local time to sit together and show retaliation is #NotOkGoogle. The stories we've been collecting will be shared, our demands will be read, and all will be in solidarity with those withstanding this chilling practice. — Google Walkout For Real Change (@GoogleWalkout) May 1, 2019

Organizers said that testimonies from employees who allegedly experienced retaliation would be read at the sit-ins. Other workers would protest by calling in sick, they said.

A spokesperson for Google declined to comment on the protests, but said the company prohibits retaliation.

"To make sure that no complaint raised goes unheard at Google, we give employees multiple channels to report concerns, including anonymously, and investigate all allegations of retaliation," said the spokesperson.

Meredith Whittaker, one of the organizers of the November walkout who claimed she was retaliated against, tweeted that hundreds of people showed up to the Google sit-in in New York City.

Hundreds of people showed up to the @google NYC anti-retaliation sit-in, planned in under 24hrs. So many brave people shared their stories. There were tears and talk of unions. #NotOkGoogle — Meredith Whittaker (@mer__edith) May 1, 2019

The company's alleged retaliation against some employees is the subject of a complaint filed with the National Labor Relations Board. It is against federal law to threaten employees with "adverse consequences" for engaging in "protected, concerted activity."

Many Google offices in Asia and Europe were closed Wednesday for May Day. Protest leaders encouraged employees there to join local marches celebrating the labor holiday but said any Google employees with the day off could participate in protests the next business day.

The sit-ins aren't the only collective action that has resulted from the coordinated Google walkouts in November.