The allegations by U.S. Republican presidential candidates that Islamic groups have a presence in Mexico "are unfounded," Foreign Secretary Patricia Espinosa said.

"There is no foundation that can can support the kinds of statements" made during the Republican presidential debate earlier this week, Espinosa said.

"We were very surprised when assertions were made during the debate without providing any kind of element of respect," the foreign secretary said, referring to allegations that members of the radical Islamic groups Hamas and Hezbollah were using Mexico to enter the United States.

Former Massachusetts Gov. Mitt Romney, a leading contender for the GOP nomination, said during Tuesday night's debate on foreign policy that Hezbollah was operating in Mexico and other Latin American countries.

"We have, right now, Hezbollah, which is working throughout Latin America, in Venezuela, in Mexico, throughout Latin America, which poses a very significant and imminent threat to the United States of America," Romney said during the debate in Washington.

While acknowledging that "these kinds of statements are made in an electoral context," Espinosa urged "greater caution" from the candidates, especially on "such delicate and important issues as these" in bilateral relations.