London (CNN) Women around the world are marking International Women's Day on Wednesday, with some wearing red to work and others taking the day off to go on strike or join rallies calling for equal rights.

International Women's Day, which started in the early 1900s, is an annual celebration recognizing women's economic, political and social achievements. It also serves to highlight the ongoing struggle for gender equality worldwide.

This year, the United Nations is calling on governments to make national commitments that address the challenges still holding women and girls back. Only 50% of working age women are represented in the labor force globally, compared to 76% of men, according to the UN. Their initiative, "Planet 50-50," aims to make gender equality a reality by 2030

"Denying the rights of women and girls is not only wrong in itself," UN Secretary-General Antonio Guterres said in a statement on Monday. "It has a serious social and economic impact that holds us all back. Gender equality has a transformative effect that is essential to fully functioning communities, societies and economies."

'A Day Without a Woman'

Crowds descend on Washington for the Women's March in January.

In the United States, some women are taking the day off from paid and unpaid labor in a strike billed as "A Day Without a Woman." The action is aimed at showing the economic importance and impact of women on society. It was organized following the Women's March on January 21, which saw huge crowds of demonstrators rally in Washington, DC, and around the nation, in a backlash against US President Donald Trump on his first full day in office.

Trump posted two tweets on Wednesday marking International Women's Day, asking others to join him in "honoring the critical role of women here in America and around the world."

On International Women's Day, join me in honoring the critical role of women here in America & around the world. — Donald J. Trump (@realDonaldTrump) March 8, 2017

Across the pond, British Prime Minister Theresa May hailed International Women's Day in Parliament, announcing the government's pledge of an additional £20 million ($24.3 million) to support organizations working to tackle domestic violence and abuse.

"As we celebrate the social, economic, cultural, and political achievements of women both here and around the world ... we also redouble our efforts to tackle the problems that women all to often still face," May said.

Women go on strike around the world

Photos: International Women's Day Demonstrators fill a barricaded space along New York's Fifth Avenue during an International Women's Day rally on Wednesday, March 8. Events have been scheduled around the world to celebrate women's accomplishments and call attention to women's issues. Hide Caption 1 of 25 Photos: International Women's Day People in Washington march near the White House from Freedom Plaza to Lafayette Park. Hide Caption 2 of 25 Photos: International Women's Day Women in Istanbul march down Istiklal Avenue. Hide Caption 3 of 25 Photos: International Women's Day A statue of a defiant girl faces Wall Street's charging bull sculpture in New York. "Fearless Girl" was installed on Tuesday by State Street Global Advisors. The asset manager designed it to call attention to its new initiative to increase the number of women on its clients' corporate boards. Hide Caption 4 of 25 Photos: International Women's Day People gather outside City Hall in San Francisco. Hide Caption 5 of 25 Photos: International Women's Day Activist Tamika Mallory sits in the back of a police van after being detained for blocking traffic outside the Trump International Hotel and Tower in New York. "Many of our national organizers have been arrested in an act of civil disobedience," tweeted the Women's March organization. "We will not be silent." Hide Caption 6 of 25 Photos: International Women's Day Melania Trump, the first lady of the United States, hosted a White House luncheon for International Women's Day. Hide Caption 7 of 25 Photos: International Women's Day Demonstrators rally in Melbourne. Hide Caption 8 of 25 Photos: International Women's Day Women in Seoul, South Korea, protest gender inequality and sexual harassment in the workplace. Hide Caption 9 of 25 Photos: International Women's Day Advocates for women's rights march in front of Parliament in Tbilisi, Georgia. Hide Caption 10 of 25 Photos: International Women's Day Women hold a banner as they protest in front of the United Nations building in Sanaa, Yemen. Hide Caption 11 of 25 Photos: International Women's Day Trade union members show solidarity for female workers outside the union headquarters in Pamplona, Spain. Hide Caption 12 of 25 Photos: International Women's Day Demonstrator Katie Bush joins a rally outside City Hall in San Francisco. She works for YouTube and got the day off to participate. "Basically I feel this administration is not representing over half the country," she said. "I hope this message goes to Trump, obviously, but also the country and the world. We have to be present and show up." Hide Caption 13 of 25 Photos: International Women's Day Brazilian airline pilot Gabriela Carneiro Duarte, third from right, walks with her all-female crew before departing for a flight in Rio de Janeiro. Hide Caption 14 of 25 Photos: International Women's Day A mandala made of salt is displayed at a shopping mall in Milan, Italy. Hide Caption 15 of 25 Photos: International Women's Day People in Bucharest, Romania, lie on the ground during a performance to raise awareness about women killed by their partners. Hide Caption 16 of 25 Photos: International Women's Day A protester in Washington holds up a sign. Hide Caption 17 of 25 Photos: International Women's Day Members of a women's group face off against female police officers as they shout anti-American slogans near the US Embassy in Manila, Philippines. Many protesters this year have turned out to voice their disagreement with the policies and rhetoric of US President Donald Trump, especially regarding women's issues. Hide Caption 18 of 25 Photos: International Women's Day A Palestinian artist applies the final touches to a street mural in Gaza City. Hide Caption 19 of 25 Photos: International Women's Day A woman helps a boy light a candle in Hong Kong. Hide Caption 20 of 25 Photos: International Women's Day A member of the Italian special police known as the Carabinieri stands at attention during an event in Rome. Hide Caption 21 of 25 Photos: International Women's Day Women shout slogans during a march in Kiev, Ukraine. Hide Caption 22 of 25 Photos: International Women's Day Women wear traditional Punjabi dresses as they dance during an event in Amritsar, India. Hide Caption 23 of 25 Photos: International Women's Day Women in Lagos, Nigeria, protest against sexual violence. Hide Caption 24 of 25 Photos: International Women's Day Commemorative T-shirts are displayed in Washington. In the United States, women were encouraged to take the day off from paid and unpaid labor in a strike billed as "A Day Without a Woman." Hide Caption 25 of 25

American women aren't the only ones taking to the streets.

In Ireland, where abortion is illegal in almost all circumstances, women and abortion rights activists wore black in a day of action dubbed "Strike 4 Repeal."

Thousands were expected to rally across the country, urging the government to put forward a referendum to repeal Ireland's eighth amendment -- a measure that places the right to life of an unborn child on equal footing with the right to life of the mother. The amendment prohibits abortion even in cases of rape, incest, or ill health of the mother, allowing it to be considered only when a woman's life is in immediate danger.

Abortion rights activists protest in Dublin.

Clare Brophy, a 30-year-old PhD student, said that she came out to strike for a referendum.

"In the eyes of Irish law, I'm equal to an unborn fetus. I'm not," Brophy said.

In Australia, thousands of demonstrators attended a rally in Melbourne, demanding economic justice and reproductive rights for women around the world.

In the Philippines, members of the women's group Gabriela Party marched to the US embassy in Manila carrying signs calling for employment and discrimination reforms.

Members of women's group Gabriela march in Manila.

A Women's Day protest caused chaos and delays in Rome, leaving some Italian commuters stranded. While not everyone welcomed the disturbance, one nun voiced her support.

"It's true that women are paid less and don't have access to the same positions and work opportunities that men do," Sister Ursula from Poland said. "This is not right because women and men are equal. God created man and woman to complete each other, with dignity and equality."

Young Indian women perform the 'Giddha' dance during Women's Day celebrations in Amritsar.

Putin congratulates women on holiday

International Women's Day is an official holiday in more than 100 countries, including in Russia, where President Vladimir Putin marked the occasion with a speech congratulating women on state television.

"You care day and night for your children, grandchildren and your family. Even today, on International Women's Day, you are still caught up in your routine, working tirelessly, always on time. We often ask ourselves, how do they manage it all?" Putin said

"We will do our utmost to surround the women we love with care and attention, so that they can smile more often," Putin added.

The Russian President traveled to a perinatal center in the western Russian city of Bryansk for the holiday -- emphasizing the more traditional roles for women celebrated in the country, such as motherhood.

In Moscow, a group of feminist activists were detained after protesting by the Kremlin walls, holding a banner reading: "Men have been in power 200 years, down with them!"