NEW YORK: US prosecutors named top Al-Qaeda leaders Wednesday in an alleged attempt to bomb New York`s subway, saying their failed plot was part of a Pakistan-based campaign against US and British cities.

The indictment dramatically broadened the case in which Afghan immigrant and Colorado resident Najibullah Zazi pleaded guilty earlier this year to conspiring to set off explosions in the metro system in 2009.

"The charges reveal that the plot... was directed by senior Al-Qaeda leadership in Pakistan and was also directly related to a scheme by Al-Qaeda plotters in Pakistan to use Western operatives to attack a target in the United Kingdom," the Department of Justice said in a statement.

At a time of growing "homegrown" terrorism incidents, the indictments underlined the US view that ruthless foreign-based Al-Qaeda groups, rather than a rag-tag and amateurish collection of US residents, are the main threat.

The indictment unsealed in a New York federal court charged five people and made clear that Zazi was not only inspired, but also directed by Pakistani-based Al-Qaeda groups.

Most prominent among the accused is Saudi-born Adnan El Shukrijumah, charged with being one of three "leaders of Al-Qaeda`s `external operations` program dedicated to terrorist attacks in the United States and other Western countries."

The justice department claims that all three of those leaders "organized" the Zazi plot, even if only El Shukrijumah is charged.

Also charged is a man identified only as Ahmad, who allegedly was the "facilitator" keeping in touch with Zazi, a former Denver Airport shuttle driver, by email.

El Shukrijumah is accused of recruiting Zazi and two other men -- one who has pleaded guilty and one who is in US custody but has not yet been tried -- between September-December 2008.

They were to "conduct suicide bombings in New York City using improvised explosive devices made from supplies such as hydrogen peroxide, acetone, flour and oil."

Ahmad then oversaw the preparations, the indictment alleges.

In a chilling final email just before leaving on his failed mission to New York from Colorado, Zazi allegedly wrote to Ahmad, using code, that his deadly plot was primed. "The marriage is ready," he allegedly wrote.

All the men charged in the indictment face life in prison if found guilty. However, El Shukrijumah remains at large, according to the justice department, with a five million dollar reward on his head, while Ahmad`s status was not immediately clear.

Further broadening the allegations, the indictment links Ahmad to an alleged bombing plot in Britain.

Ahmad was similarly communicating by email on behalf of the Al-Qaeda leadership with Abid Naseer and Tariq Ur Rehman, two men detained in Britain in 2009 on suspicion of planning a bomb plot in the northeastern city of Manchester.

In their communications they also used the same code, the justice department says, referring to a "large `wedding` for numerous guests between April 15 and 20, 2009, and that `Ahmad` should be ready."

Both Naseer, who was arrested Wednesday by British police following a US extradition request, and Rehman, who is not in custody, are named in the indictment.

The fifth man named in the indictment is Adis Medunjanin, an associate of Zazi who is awaiting trial in New York.

The new charges "underscore the global nature of the terrorist threat we face," said prosecutor David Kris.

"They further reflect the effectiveness of mutual investigations and cooperation with our global partners in disrupting terrorism threats," added Kris, assistant attorney general for national security at the Department of Justice.

Last month a Pakistani-American, Faisal Shahzad, pleaded guilty in a New York federal court to attempting to set off a car bomb in the city`s teeming Times Square.

He said he was acting in vengeance for US military assaults in Afghanistan and Iraq.

Zazi also said he was "sacrifice" himself "to draw the attention to what he said were US crimes in Afghanistan."

He pleaded guilty in February to the three charges of conspiracy to use weapons of mass destruction, conspiracy to commit murder in a foreign country and providing material support to the Al-Qaeda Islamist network.

He told the federal court in Brooklyn that his plans to blow up New York targets just after the eighth anniversary of the 9/11 attacks included "mortal operations" in the underground train system.

BDST: 0845 HRS, July 8, 2010