WASHINGTON – The Obama administration declared the ultra-violent street gang MS-13 to be an international criminal group on Thursday, an unprecedented crackdown targeting the finances of the sprawling U.S. and Central American gang infamous for hacking and stabbing victims with machetes.

The Treasury Department formally designated MS-13, or Mara Salvatrucha, a transnational criminal organization. The aim is to freeze it out of the U.S. financial system and seize what are estimated to be millions of dollars in criminal profits from drug and human smuggling and other crimes committed in this country.

The gang was founded by immigrants fleeing El Salvador’s civil war more than two decades ago. Its founders took lessons learned from that brutal conflict to the streets of Los Angeles and built a reputation as one of the most ruthless and sophisticated street gangs, according to Immigration and Customs Enforcement Special Agent Jason Shatarsky.

With as many as 10,000 members in 46 states, the gang has expanded far beyond its initial roots. Members are accused of major crimes including murder, kidnapping, prostitution, drug smuggling and human trafficking.

The group established itself in Los Angeles before spreading across the U.S., said Shatarsky, an MS-13 expert assigned to ICE’s national gang unit. The group’s violence – using a machete to hack a victim to death or shooting someone in the head in broad daylight, for instance – surprised authorities and even rival gangs.

“They saw a level of violence that hadn’t been seen before,” Shatarsky said, adding that as the gang has expanded it has also become more sophisticated than many rivals.

The gang, which is allied with several of Mexico’s warring drug cartels, has a strong presence in Southern California, Washington and Northern Virginia, all areas with substantial Salvadoran populations. Shatarsky said its members target residents and business owners for extortion, among other crimes. The gang is also active throughout Central America and in parts of Mexico. Authorities in Europe have reported evidence of MS-13 expanding operations there.

Among the most high-profile killings attributed to MS-13 in Virginia was the 2003 slaying of a pregnant teenager who had become an informant. Brenda Paz, 17, was stabbed to death and her body was left along the banks of the Shenandoah River. Gang members have also been linked to the 2007 execution style shooting deaths of three friends in a schoolyard in Newark, N.J. One victim was slashed with a machete before being shot. Six people have been charged in the case.

By labeling MS-13 an international criminal organization subject to sanctions by the Treasury Department’s Office of Foreign Assets Control, the government hopes to stymie the gang’s ability to funnel money back to its leaders in El Salvador or launder criminal proceeds through otherwise legitimate businesses.

George Grayson, an expert on Mexico’s Los Zetas drug cartel who has also studied other criminal organizations, said the Treasury sanctions are likely to be successful throttling the group’s finances in the U.S. but may not affect its operations in El Salvador or the rest of Central America. With the gang having significant numbers of members operating outside the U.S., he said, it may be hard to have as significant an impact as the government wants.

“You’ve got to have cooperation with the Central American authorities,” said Grayson, a professor at the College of William & Mary and a senior associate at the Center for Strategic & International Studies in Washington.

The Treasury Department’s undersecretary for terrorism and financial intelligence, David S. Cohen, said that while no specific members of the gang have been listed as part of the group’s sanction, anyone identified as a gang member or associate trying to do business with gang members could be subject to criminal prosecution.

The government is also making it more difficult for gang members to use banks and wire transfer services to move profits from the group’s crimes.

ICE Director John Morton described the designation as a “powerful weapon” for his agency’s effort to dismantle the gang. The action “allows us to strike at the financial heart of MS-13,” he said.

Other international criminal groups that have been subject to similar sanctions by the Treasury Department include the Yakuza, a Japanese organized crime group, and the ruthless Mexican drug cartel, Los Zetas