Agents take a person into custody during operation “Cross Check” on March 28 in New Jersey. The Obama administration said it arrested more than 3,100 immigrants who were illegally in the country and who were convicted of serious crimes or otherwise considered fugitives or threats to national security. (U.S. Immigration and Customs Enforcement/AP Photo)

U.S. Immigration and Customs Enforcement officials said Monday that they had arrested more than 3,100 criminals and others living in the country illegally, the largest such effort in the agency’s history, adding fuel to the national debate over the Obama administration’s stepped-up deportation policies.

The six-day operation — dubbed “Cross Check” — nabbed 3,168 offenders across the nation, including in all 50 states, three territories and the District of Columbia. Of those, 1,477 taken into custody had felony convictions such as murder, manslaughter, attempted murder, kidnapping, child abuse, assault and other offenses.

“This is part of our effort to prioritize our immigration enforcement efforts,” said John Morton, the agency’s director. “As a matter of public safety, we start first and foremost with criminal offenders.”

The wide-ranging sweep, the third in two years, included 131 arrests in Virginia — 20 in the city of Alexandria — 53 in Maryland and 11 in the District of Columbia.

The Obama administration has faced criticism from across the political spectrum for tightening its controls on illegal immigration. The administration has deported about 1 million people in the past three years, some 400,000 yearly, a record-setting pace.

Advocates for the nation’s estimated 12 million illegal immigrants expressed concern about Monday’s raids, saying that while they supported the premise of targeting criminal aliens, large roundups tend to sweep in less serious offenders who may have committed only minor violations.

In addition to the convicted criminals, 698 of those arrested were what authorities call “immigration fugitives,” which means that they were previously ordered to leave the country but failed to depart. Others had committed misdemeanor offenses.

“The concern is, are we doing this with a scalpel or a sledgehammer?” said Laura Lichter, president-elect of the American Immigration Lawyers Association, a group of lawyers who practice immigration law. “Just because someone had an encounter with the criminal justice system — that could have been just for driving without a license.”

But Morton dismissed such concerns, noting that all of those arrested had either criminal backgrounds or a previously outstanding immigration order.

“I wouldn’t agree with that basic premise to start with,” Morton said. “While many of the people who did have convictions had misdemeanors, a significant portion of those had multiple misdemeanor convictions.”

Among the dozen serious offenders named Monday by ICE officials was Emmanuel Awanda, 31, a native of Cameroon. Awanda was picked up in Amherst, a tiny town in south-central Virginia, where he was living after being convicted of drug distribution and firearms charges.

Others arrested included Ignacio Franco-Galvez, 43, a self-admitted member of the Norteno gang back in the United States illegally for the third time and living in Sacramento, and Jose Angel Duran-Ramos, 66, a native of Mexico and convicted murderer living in El Paso. Those arrested will be kept in civil detention centers, where they can either ask for a hearing before an immigration judge or voluntarily leave the country, an ICE spokesman said.

Although those arrested would return to 116 countries, the large majority were from Mexico and other Central American countries. Immigration advocates said that was not a surprise but that it highlights the delicate spot Obama finds himself in with Latino voters as he heads into the general election campaign.

Two-thirds of Hispanic voters supported the president in 2008, and Republicans have yet to make significant strides in winning them over.

But Frank Sharry, executive director of America’s Voice, an immigration reform advocacy group, said the continuing raids will hurt Obama with Hispanic voters.

“This is a personal issue, particularly for Latino immigrant voters who made a huge difference for Obama in 2008 and will play a huge factor this year if they turn out in swing states,” Sharry said.

Advocates for tougher enforcement, meanwhile, have accused the administration of using the raids to appeal to independents and moderates while retaining the support of Obama’s political base.

“This is obviously part of the administration’s effort to convince the American public that they are serious about immigration enforcement, while assuring advocates for illegal aliens that, ‘Hey, you guys have nothing to worry about,’ ” said Ira Mehlman, spokesman for the Federation for American Immigration Reform, which advocates tougher enforcement.

Researcher Magda Jean-Louis contributed to this report.