MEXICO CITY (Reuters) - Members of a U.S.-Mexican religious community who lost relatives in a gangland massacre this month have come under fire from supporters of Mexico’s government for pressing the United States to declare drugs cartels terrorist groups.

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Three mothers and six children of dual U.S.-Mexican nationality were shot to death in a brutal attack by suspected drug cartel gunmen in the northern state of Mexico, sparking outrage and condemnation in the United States.

The victims belonged to breakaway Mormon families who came to Mexico from the United States decades ago, and some of their U.S. relatives launched a petition over the weekend asking the government to declare the drug cartels terrorist organizations.

U.S. President Donald Trump said he would have the gangs designated terrorist groups, stirring fears that he could send the U.S. military across the border to take them out, ramping up pressure on Mexico ahead of his re-election bid in 2020.

Mexican President Andres Manuel Lopez Obrador said he would not accept any intervention from foreign powers.

Many social media users expressed support for Lopez Obrador and heavily criticized the petition directed to the White House, calling it treasonous and accusing the families of wanting to create a pretext for a U.S.-led invasion.

Twitter posts in Mexico often carried a Spanish language hashtags referring to the LeBaron family as traitors and asking them to leave the country.

“They’ve got double nationality so why don’t they return to their country instead of selling us out,” one such post read. “All Mexicans feel unsafe but that doesn’t make us ask for foreign intervention.”

Alex LeBaron, a former Mexican congressman and relative of some of the victims, called the accusations “baseless” and “insulting” in an interview.

“They’re terrorists, these cartels, whether they are declared as such or not,” LeBaron said. Previously, he rejected a U.S.-led intervention and instead called for cooperation to improve security for all Mexicans.

The La Mora community in Sonora, where members of the LeBaron as well as the Miller and Langford families live, is still in mourning. This year, they have not followed their tradition of opening their houses to locals on Thanksgiving.

On Dec 1, which marks the first anniversary of Lopez Obrador taking office, members of the community plan to protest violence in Mexico City.