The U.S. Immigration and Customs Enforcement agency is planning to round up thousands of immigrant families who have illegally entered the country since the start of last year and subsequently deport them, according to media reports.

The nationwide campaign could begin as early as the first week of January, The Washington Post reported, citing various sources who spoke on condition of anonymity because the operation has not yet received final approval from the U.S. Department of Homeland Security.

The Wall Street Journal also cited several sources as saying the decision to conduct the operation was aimed at discouraging Central American migrants, including unaccompanied minors, from fleeing their countries to reach the United States.

DHS spokeswoman Marsha Catron declined to comment on ICE's plans but told the Post that DHS Secretary Jeh Johnson "has consistently said our border is not open to illegal immigration."

"If individuals come here illegally, do not qualify for asylum or other relief, and have final orders of removal, they will be sent back," she added.

In the summer of 2014, the U.S. experienced a wave of child immigration, receiving 10,000 unaccompanied minors a month, mainly from Guatemala, El Salvador and Honduras.

More than 12,000 people were caught crossing the U.S. border illegally in October and November of this year, nearly three times the number - 4,500 - apprehended during the same months of last year.

Reports that the ICE intends to immediately deport hundreds of people who have already received removal orders have prompted criticism from the two leading Democratic presidential hopefuls.

The Hispanic media director for Hillary Clinton's campaign, Jorge Silva, said the former secretary of state had "real concerns" about the reports, especially at a time when families were gathering during the holiday season.

She believes it is essential for everyone to have a full and fair hearing and for the United States to provide refuge to those who need it, he added.

Meanwhile, the campaign of Clinton's main rival for the Democratic nomination, Vermont Sen. Bernie Sanders, also criticized the alleged ICE operation.

"I am very disturbed by reports that the government may commence raids to deport families who have fled here to escape violence in Central America," Sanders said in a statement.

"As we spend time with our families this holiday season, we who are parents should ask ourselves what we would do if our children faced the danger and violence these children do? How far would we go to protect them?" the senator added.