New York: An Afghan-born airport worker was charged with planning a massive bombing campaign as authorities said they had foiled a string of similar but unrelated terror plots across the United States.
Najibullah Zazi, 24, was indicted in New York on charges of conspiring to launch a wave of attacks using homemade bombs constructed with chemicals bought in large quantities from beauty parlor supply stores.
An unsealed grand jury indictment alleged Zazi had received bomb-making instruction in Peshawar, Pakistan, researched homemade explosives in Colorado and drove to New York intent on unleashing carnage.
Attorney General Eric Holder said the case was far from closed despite the arrest of Zazi, who was believed to be working with unidentified conspirators.
"We are investigating a wide range of leads related to this alleged conspiracy, and we will continue to work around the clock to ensure that anyone involved is brought to justice," Holder said.
"We believe any imminent threat arising from this case has been disrupted, but as always, we remind the American public to be vigilant."
As details of the Zazi case emerged, authorities in Illinois and Texas announced arrests following separate undercover investigations which involved militant Islamists attempting to blow up buildings with car bombs.
A 29-year-old Illinois man, Michael Finton, known as Talib Islam, was arrested after driving a vehicle packed with inactive explosives to a federal building and courthouse in Springfield and attempting to detonate it.
Justice department officials said the arrest was the final act of an undercover operation lasting several months.
Details of the case were strikingly similar to an investigation later disclosed in Dallas, where a 19-year-old Jordanian man was arrested on charges of trying to bomb up a 60-story glass skyscraper in the city`s downtown.
Authorities said Hosam Maher Husein Smadi was arrested after a sting operation involving FBI agents posing as members of an Al Qaeda sleeper cell.
As in the Illinois case, federal agents pounced after Smadi had driven an inert car bomb to the targeted buildings.
Justice authorities in Texas and Illinois stressed however there were no links between their investigations and the Zazi case in New York and Denver.
In other unrelated investigations, authorities in New York said they had charged a man with seeking to commit murder in a foreign country after traveling abroad and trying to join a radical Islamic group.
New charges were also laid against three men in North Carolina already in custody for plotting "homegrown" attacks against the United States.
Analysts speculated that publicity surrounding the Zazi case, which has been described as the most serious terrorist plot in the United States since the 9/11 attacks of 2001, may have nudged law enforcement agencies into action.
Carl Tobias, a law professor at the University of Richmond who has studied investigations into terrorism around the United States, said developments in the myriad cases were "to some extent coincidental."
"I think what`s been happening in New York and Colorado has sensitized everyone, including people in the government, and that may have stepped up the pressure to move on some other matters.
"Maybe all of these counter-terrorism agencies are being hyper-sensitive. But it is odd to see so many cases in such a short space of time."
R.P. Eddy, a senior fellow for counter-terrorism at the Manhattan Institute, told CNN the cases in Dallas and Illinois -- one involving an illegal alien, the other a US citizen -- highlighted the range of threats facing authorities.
"These are different types of attacks," Eddy said. "Hopefully we finally realize we have to pay attention to every part of the spectrum."
Zazi, who is to be transferred from Denver to New York, remains in detention and faces life in prison if convicted.
Meanwhile, New York imam Ahmad Wais Afzali, who is charged with lying to investigators on the case, was ordered released by a Brooklyn federal judge on 1.5 million dollars bail.
Zazi`s father in Colorado, also charged with lying, has likewise been ordered free on bail.