A failed plot to set off bombs in the New York subway system last year was part of a larger al-Qaida terrorist conspiracy that planned a similar attack in England, federal prosecutors said Wednesday.
In a superceding indictment unsealed Wednesday, prosecutors added several al-Qaida figures to the case, including Adnan Shukrijumah, an FBI most-wanted terrorist.
Shukrijumah, one of the al-Qaida leaders in charge of plotting attacks worldwide, was directly involved in recruiting for and planning the New York attack, prosecutors said.
In that case, three U.S. citizens were arrested in September 2009 before they could carry out a trio of suicide bombings in Manhattan, according to prosecutors. Najibullah Zazi and Zarein Ahmedzay have pleaded guilty and admitted planning to detonate homemade bombs on the subway during rush hour.
A third man, Adis Medunjanin, awaits trial. Prosecutors added new terrorism charges against him Wednesday.
There was no immediate response to a phone message left with Medunjanin's attorney.
Attorney General Eric Holder has called the New York subway plot one of the most dangerous since 9/11.
Shukrijumah, 34, one of the world's most-wanted terrorism suspects with a $5 million reward on his head, allegedly recruited the attackers. He is not in custody and is believed to be hiding along the Pakistan-Afghanistan border, U.S. officials told WNBC-TV in New York.
Two other senior al-Qaida leaders — Saleh al-Somali and Rashid Rauf — worked with Shukrijumah to plan the attacks, according to the U.S. Department of Justice. Both Rauf and al-Somali are believed to have been killed about a year apart in attacks by U.S. drones in Pakistan.
Two other men indicted Wednesday — Abid Naseer and Tariq Ur Rehman — were linked to a companion plot in England.
Naseer was arrested in northeast England on Wednesday and taken to London for a court appearance.
"Abid Naseer, 24, has been arrested in the United Kingdom pursuant to a provisional arrest warrant issued on July 7, 2010, at the request of the United States government,” a London police spokesman told the ITN television network.
A fifth suspect, who acted as a go-between in the two plots from Peshawar, Pakistan, is known only as "Ahmad," "Sohaib" or "Zahid," it said. The Associated Press, which first revealed the alleged involvement of Shukrijumah in the New York City plot last week, also reported that "Ahmad" is in custody in Pakistan.
All the defendants were charged with multiple terrorism violations.
"These charges underscore the global nature of the terrorist threat we face," said David Kris, the Justice Department's top national security prosecutor.
The new indictment charging a conspiracy to use weapons of mass destruction alleges that Shukrijumah and Ahmad recruited Zazi, Ahmedzay and Medunjanin in 2008 to receive training from al-Qaida in the Waziristan region of Pakistan.
Once the three former high school classmates from Queens returned to the United States in early 2009, it adds, Ahmad traded coded e-mail messages with both Zazi and Naseer.
Prosecutors say in one message, Naseer told Ahmad he was planning a large "wedding" — code for attack. Likewise, Zazi e-mailed Ahmad that "the marriage is ready" shortly before he drove from Colorado to New York City carrying bomb-making components in September 2009, they add.
Naseer and Rehman were first arrested on April 8, 2009, in the United Kingdom in raids that took place after a blunder by former Metropolitan Police Assistant Commissioner Bob Quick, who accidentally showed secret documents outside Downing Street.
In connection with the arrests, U.K. authorities conducted searches and found large quantities of flour and oil that were believed intended for use in explosives. Investigators also found surveillance photographs of public areas in Manchester and maps of Manchester’s city center posted on the wall, with one of the locations from the surveillance photographs highlighted, according to a Department of Justice press release.
Nonetheless, all 12 suspects were released without charge, with 11 of the men transferred into the custody of the U.K. Border Agency. The British government attempted to deport Naseer and a second man, Ahmed Faraz Khan, 26, to Pakistan, but a judge blocked it on the grounds they could be tortured.
Naseer, who was described in court as an al-Qaida operative who "posed and still poses" a significant security threat to Britain, was released, but Home Secretary Theresa May said at the time that "all possible measures" were being taken to ensure that he and Khan could not engage in terrorist activity. Such measures could have included control orders, surveillance and other efforts to restrict their movements and activities.
Andrew Hayman, a former Scotland Yard assistant commissioner and now an NBC News terrorism consultant, called the arrest of Naseer “very significant.”
“This was a man who was part of an arrest in Manchester in the northern part of the U.K. and it was a cell which was suspected of plotting to actually attack that city.”
Shukrijumah's alleged involvement also is a significant development.
After 9/11, Shukrijumah was seen as one of al-Qaida's best chances to attack inside the U.S. or Europe, captured terrorist Abu Zubaydah told U.S. authorities. Shukrijumah studied at a community college in Florida but when the FBI showed up to arrest him as a material witness to a terrorism case in 2003, he already had left the country.
In 2004, then-Attorney General John Ashcroft called Shukrijumah a "clear and present danger" to the United States.
The Associated Press, msnbc.com's Brinley Bruton and WNBC reporter Jonathan Dienst contributed to this report.