Mexican officials said on Thursday they planned to file criminal complaints in the United States over the deaths of several Mexican nationals during immigration operations, in the nation’s most confrontational protest yet against President Trump’s immigration policies.

Roberto Velasco Álvarez, Mexico’s foreign affairs minister, announced the move in a news conference on Thursday, two days after an Immigration and Customs Enforcement agent fatally shot a Mexican man who had lived and worked for decades in the United States and was trying to obtain legal residency.

Mr. Velasco said Mexico would file the complaints with U.S. state prosecutors and the U.S. Department of Justice, requesting criminal investigations into the deaths of 14 Mexican citizens in immigration detention centers and of three others during enforcement raids under the current administration.

In a statement, the U.S. Department of Homeland Security did not deny Mexico’s tally of its citizens who have died in the department’s custody, but rejected accusations that migrant deaths have spiked since Mr. Trump returned to office. The U.S. Department of Justice did not respond to a request for comment.

In Mr. Trump’s second term, relations with Mexico have grown increasingly strained, as he has lobbed verbal attacks and threats of tariffs at the country.

His administration has also increased pressure on Mexico to crack down on corrupt officials and cartels, threatening military action against the criminal organizations. President Claudia Sheinbaum of Mexico has pushed back, stressing sovereignty as a pillar of the two countries’ relationship. U.S. prosecutors have indicted 10 current and former Mexican officials — including a sitting governor — and demanded their detention for extradition. Mexico has refused to comply, arguing insufficient evidence against them.