The highly publicized raids by US immigration authorities to detain and deport illegal immigrants appeared not to materialize over the weekend and on Monday.

Immigrant advocacy groups in several states reported no arrests had been made, but President Donald Trump told reporters at the White House on Monday that "the ICE raids were very successful…many, many were taken out on Sunday you just didn't know about it."

The raids by the US Immigration and Customs Enforcement (ICE) were to start on Sunday and continue through Thursday and target at least 2000 undocumented immigrants in Atlanta, Baltimore, Chicago, Denver, Houston, Los Angeles, Miami, New York and San Francisco.

But Jorge-Mario Cabrera, director of communications for the Coalition for Humane Immigrant Rights in Los Angeles, told China Daily: "No. There hasn't been any of the supposed arrests that were threatened [here.] There have been other arrests. [Our advice] has always been the same. To not open the door. To remain quiet. To be respectful of authority. Not run away and not sign any papers."

The American Civil Liberties Union of New York tweeted: "We've heard some reports of ICE at subway stations, but none have been substantiated."

New York Mayor Bill de Blasio said on Twitter on Sunday: "We've followed up on every report today and so far, have no confirmed ICE activity."

Before they were to begin, the mayors of the California cities of Oakland, San Jose and San Francisco — all sanctuary cities — had voiced their opposition. San Francisco Mayor London Breed said her city would not cooperate with ICE.

Trump stressed last week that the raids would lead to mass deportation and detention of migrants, prompting fear among immigrant communities.

Mark Morgan, acting director of ICE later clarified that the number would be closer to 2,000 and would focus on recently arrived undocumented families who had final removal orders from immigration courts.

Ken Cuccinelli, acting US Citizenship and Immigration Services director, told CNN on Monday that he didn't know how many people had been arrested because the acting director of ICE hadn't told him. Cuccinelli said this was "presumably because operational details are kept contained within the agency executing the operation, as they should be."

On Monday, the Trump administration unveiled sweeping changes to the asylum rules, the latest attempt to restrict the influx of migrant families coming to the United States.

The Justice and Homeland Security departments announced plans to deny asylum to most Central American migrants and others who travel by land to enter the US from the Mexican border.

Under the proposal, migrants who do not apply for asylum in the first country they get to on their way to America's southwest border would not be offered protection. Migrants who prove they did apply but were denied, will still be allowed to seek asylum at the US border.

The rule will go into effect on Tuesday and is another attempt to limit asylum seekers, say critics.

The ACLU said it planned to sue the Trump administration over this "unlawful" rule.