Hector Xavier MonsegurLaw enforcement officials on two continents arrested top members of the computer hacking group LulzSec early this morning, acting on evidence provided by the organization’s leader – whom sources say had been secretly working for the government for months.

Three members of the group were arrested and two more were charged with conspiracy.

A formal indictment charging the suspects – who include two men from Great Britain, two from Ireland, and an American in Chicago – is expected to be unsealed this morning in the Southern District of New York.

“This is devastating to the organization,” said an FBI official. “We’re chopping off the head of LulzSec.”

LulzSec, an offshoot of the hacktivist group known as Anonymous, was allegedly led by 28-year-old Hector Xavier Monsegur.

Working under the Internet alias “Sabu”, the unemployed father of two allegedly commanded an international team of thousands of hackers from his headquarters in a public housing project on New York’s Lower East Side. After the FBI identified Monsegur last June, he became a cooperating witness.

“They caught him and he was secretly arrested and now works for the FBI,” said one source close to Sabu.

On August 15, Monsegur pleaded guilty to 12 hacking-related charges and information documenting his admissions is expected to be unsealed in Southern District Court today.

As a result of Monsegur’s cooperation with authorities, the remaining top-ranking members of LulzSec were arrested Tuesday morning.

The five charged in the LulzSec conspiracy indictment were identified as: Ryan Ackroyd (A.K.A. “Kayla”) and Jake Davis (A.K.A. “Topiary”), both of London; Darren Martyn (A.K.A. “pwnsauce”) and Donncha O’Cearrbhail (A.K.A. “palladium”), ┬áboth of Ireland; and Jeremy Hammond (A.K.A. “Anarchaos”), of Chicago.

Hammond was arrested on access device fraud and hacking charges and is thought to have been the key individual behind the December hack on U.S. security company Stratfor. Millions of emails were stolen and then published on Wikileaks.

Hammond will be charged in a separate indictment, and he was listed as a member of Anonymous.