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Presidential candidate Herman Cain is catching heat from Hispanic advocacy groups for suggesting the U.S. construct an "electrified" border fence to keep out illegal immigrants.

Though Cain said afterward he was just kidding, the group America's Voice put out a statement Monday calling it "no laughing matter."

"Cain may have been 'joking,' but suggesting that murder is a way to address illegal immigration just isn't funny," director Frank Sharry said in the statement.

Cain, at a campaign event in Tennessee on Saturday, defended the idea of building a barbed-wire fence along the border, "electrified, with a sign on the other side that says it can kill you."

The Republican candidate then dismissed criticism that he's being "insensitive," saying "what's insensitive is when they come to the United States across our border and kill our citizens."

Asked about the remarks on NBC's "Meet the Press," Cain said he was joking.

"That's not a serious plan. No, it's not," he said. "That's a joke. I've also said America needs to get a sense of humor. That was a joke, OK."

On Monday, Cain reversed course again, saying he takes ownership of his idea, which he described earlier as "a combination of a physical fence, technology, and in some terrible areas we might have to put troops there."

Rep. Charles Gonzalez, D-Texas, chairman of the Congressional Hispanic Caucus, said he sees "nothing funny" about Cain's so-called joke.

"Whether or not he made his comments in jest, Mr. Cain's words show a lack of understanding of the immigration issues our country is facing and a staggering lack of sensitivity. Surely, Mr. Cain understands the duty that candidates have to offer responsible policy proposals," he said in a statement. "Leave the comic routines to the professional comedians."