The demonstrators called for an end to the Tel Aviv regime's occupation of Palestine in the rallies held on Sunday.
In the British capital, the demonstration, titled "Nakba 75 – End Apartheid, End the Occupation", gathered outside the BBC headquarters before the participants made their way to Downing Street, the official residence of the prime minister.
The event was organized by the Palestinian Forum in Britain, Friends of al-Aqsa, the Palestine Solidarity Campaign (PSC) and the Muslim Association of Britain.
"The Nakba was not just a singular event, today we are still living the effect of the Nakba," Leanne Mohammed, a British Palestinian activist attending the rally, told Middle East Eye (MEE).
"Seventy-five years ago my family was expelled from their home in Haifa, Palestine, by Zionist militias. They ended up as refugees in Lebanon. Three-quarters of a century later they are still living in that same refugee camp," she said.
In a post on its website, the PSC said the Nakba Day is marked not just as a historical event but as a "continuing process of oppression enacted over the past 75 years through ongoing colonization of land, enforcement of apartheid and military occupation."
Jeremy Corbyn, the former leader of the Labour Party and a lifelong campaigner against the Israeli regime's occupation of Palestine, participated in the London march.
"Today we marched through London to mark the 75th anniversary of the Nakba and speak out against the ongoing dispossession of the Palestinian people. End the occupation. Free Palestine," Corbyn tweeted.
Israeli forces occupied more than 78 percent of historic Palestine and expelled at least 750,000 Palestinians from their lands and homes between 1947 and 1949.
Many young Palestinians joined the rally, stressing the need to continue to remember Nakba Day.
"They say 'the old will die, the young will forget', and for my generation of Palestinians we have proven that no one has forgotten and, if anything, our existence is our resistance," one demonstrator told MEE.
Meanwhile, nearly a thousand people dressed in red, green, white, and black gathered in the heart of Bay Ridge, Brooklyn, on Saturday to mark Nakba Day, among them Salma Abdallah, who stood among the people surrounded by Palestinian flags.
Both young and old people in New York City proudly had keffiyehs draped around their shoulders, wrapped around their heads, and tied around their necks, chanting, "Free, Free Palestine" and "From the river to the sea, Palestine will be free."
"Living in upstate New York, I have never seen anything like this in person. It was always on social media," a participant, named Abdallah, told the Middle East Eye. "Last year, I vowed to witness one of these rallies. And now I am here, aren’t I?”
The Arab community in Bay Ridge also marked Nakba Day with organizers emphasizing that it was more than just a protest. Rather, it was a celebration of Palestinian resistance, life, culture and the ongoing struggle for Palestinian liberation.
"It is a community gathering to assert our power and show NYC that we stand with Palestine from the river to the sea, and we support Palestinian resistance and liberation by any means necessary,” Within Our Lifetime, the organizer for the event, wrote on social media.
Over 20 organizations including Samidoun, the Palestinian Prisoner Solidarity Network; the Palestinian Youth Movement; American Muslims for Palestine; and the Black Alliance for Peace sponsored the event.
Meanwhile, a demonstration was held in Dublin, the capital and largest city of Ireland, to mark the Palestinian Nakba.