The government of El Salvador on Sunday offered advice to citizens living illegally in the United States, where immigration authorities have vowed to crack down on undocumented migrants.

“Immigration agents have to present you with an order that has been signed by a judge in order to enter your home,” read the information provided by the foreign ministry.

“If you are detained by an immigration agent, remain calm,” the statement from the Salvadoran government continued.

“If you have immigration papers, present them. If not, ask immediately to contact your attorney or the nearest consulate of El Salvador.”

The advice followed news reports last week that President Barack Obama’s administration is planning a vast operation to round up and expel undocumented migrants — including families who last year fled drought and violence in Central America.

News reports said the crackdown could begin as early as Monday and would target hundreds of families living in the US whose asylum requests had been rejected.

Any such US action would be hugely controversial, with immigration one of the hottest topics in the 2016 presidential campaign and rights groups expressing grave concern at the planned deportations.

Republican presidential frontrunner Donald Trump claimed on Twitter that the plans were the outcome of pressure he had brought to bear on the migration issue.

In contrast, Democratic frontrunner Hillary Clinton’s campaign said she had “real concerns” on the matter.

The flow of Central American families and unaccompanied children crossing into the United States from Mexico slowed in early 2015, but the numbers surged again in October and November.

A Salvadoran foreign ministry source told AFP that the nation’s consulates in the US were bracing for an influx of requests for assistance from citizens residing in America.

Refugee rights activists argue that migrants from Central America were fleeing corruption, gang violence and drought and should be treated as refugees.

In El Salvador, a country of around six million, 6,065 homicides were reported between January and November last year, up from 3,924 for the whole of 2014.

But a government spokeswoman on Immigration and Customs Enforcement told AFP that Homeland Security 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 consistent with our laws and our values,” spokeswoman Gillian Christensen said.