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MEXICO CITY — Wide-spread anti-Donald Trump demonstrations were held in 18 cities across Mexico on Sunday, marking the country’s first such protests since the U.S. president’s inauguration less than a month ago.

The principle behind them was simple: a show of national unity against Donald Trump.

Protest organizer Maria Elena Morera, said the event, which also took place in Monterrey, Puebla and Tijuana, was not aimed at Americans generally but at Trump’s policies.

Protesters at an anti-Trump demonstration in Mexico City on Feb. 12. Mariana Atencio

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The march, Morera said, was “in favor of the firmness that Mexico must have in all negotiations, so that all negotiations affecting the Mexican people and Mexicans in the United States are determined by the Mexican government.”

A post on the website of another organizer, the group Vibra Mexico, said that it was "time for Mexican citizens to join forces and unite our voices to show our disgust and outrage at the efforts of President Trump and also contribute to finding practical solutions to the challenges they imply."

Perhaps surprisingly, Mexicans hadn’t taken to the streets en masse to protest Trump before today, even after being the focus of Trump’s critical policies and rhetoric, especially the building of a border wall and an executive order on immigration.

But images of Mexican nationals being deported from the U.S. — in particular Guadalupe Garcia de Rayos, a 36-year-old mother of two who had falsified a social security number — galvanized Mexicans here.

What's it like to live in the US for 20 years of your life without papers, then going back to Mexico? 'Scary' says this Dreamer @NBCNews pic.twitter.com/7RW9q80NmL — Mariana_Atencio (@marianaatencio) February 12, 2017

“I feel disgusted. Quite frankly, you have my community members being yanked from their homes, the streets and their jobs,” said Yovany Díaz, a 25-year-old DREAMer who self-deported back to Mexico.

Some 70 organizations were involved in the rallies, including Amnesty International, Mexico's National University, business and community organizations and numerous young activists.

A protester at an anti-Trump rally in Mexico City on Feb. 12. 2017. Mariana Atencio

In Mexico City, 11,000 people marched along Reforma Avenue to the iconic Angel of Independence with banners that called the U.S. president "Twitler" and read, simply, "Stop Trump."

However, some demonstrators choose not to protest after encountering those supporting President Enrique Peña Nieto, underlining ideological fractures inside the country between those who support the Mexican president and those who oppose him. Peña Nieto's approval ratings are the lowest they've been since he took office.

Some argued that attending the rallies, partly organized by “Mexicanos Unidos,” a group known to favor Peña Nieto, legitimizes his government.

And high profile journalists like Gerardo Villamil from the publication “Proceso” warned against the rallies, arguing the focus is just on criticizing Trump and doesn't offer any solutions to the current crisis.

The Mexican government has reiterated it will not pay for the wall, while at the same time it has tried to maintain a conciliatory tone toward Trump. But judging from the scene around the country Sunday, many Mexicans have had enough of that.