The US has thwarted a plot by al-Qaeda's affiliate in Yemen to bomb an airliner around the one-year anniversary of the killing of Osama bin Laden, the country's National Security Council has confirmed to Al Jazeera.
"Initial exploitation indicates that the device is very similar to IEDs that have been used previously by al-Qaeda in the Arabian Peninsula"
- Federal Bureau of Investigation (FBI)
US media reports on Monday said the plot involved an upgrade of the underwear bomb that failed to detonate aboard a jetliner over Detroit, Michigan, on December 25, 2009.
President Barack Obama "was assured that the device did not pose a threat to the public," Caitlin Hayden, National Security Council deputy spokeswoman, said.
Obama, who had been informed of the plot in April, had however directed agencies "to take whatever steps necessary to guard against this type of attack" and had been regularly briefed by his national security team.
Separately, the Department of Homeland Security (DHS) said there was no active plot against the US at this time.
"We have no specific, credible information regarding an active terrorist plot against the US at this time," DHS spokesman Matt Chandler said.
'New and refined'
This new bomb was also designed to be used in a passenger's underwear, but this time al-Qaeda developed a more refined detonation system, US officials said on Monday.
The Federal Bureau of Investigation (FBI) is examining the latest bomb to see whether it could have passed through airport security and brought down an airplane, officials said.
They said the device did not contain metal, meaning it probably could have passed through an airport metal detector. But it was not clear whether new body scanners used in many airports would have detected it.
The would-be suicide bomber, based in Yemen, had not yet picked a target or bought his plane tickets when the Central Intelligence Agency (CIA) stepped in and seized the bomb, officials said. It is not immediately clear what happened to the alleged bomber.
"As a result of close co-operation with our security and intelligence partners overseas, an improvised explosive device (IED) designed to carry out a terrorist attack has been seized abroad," the FBI said in a statement.
"Initial exploitation indicates that the device is very similar to IEDs that have been used previously by al-Qaeda in the Arabian Peninsula (AQAP) in attempted terrorist attacks, including against aircraft and for targeted assassinations," it added.
The AP news agency learned about the thwarted plot last week, but agreed to White House and CIA requests not to publish it immediately because the sensitive intelligence operation was still under way.
Once those concerns were allayed, the AP decided to disclose the plot on Monday despite requests from the Obama administration to wait for an official announcement on Tuesday.
US officials, who were briefed on the operation, insisted on anonymity to discuss the case.
It is not clear who built the bomb, but, because of its sophistication and its similarity to the Detroit bomb, authorities suspected it was the work of master bomb maker Ibrahim Hassan al-Asiri.
Al-Asiri constructed the first underwear bomb and two others that al-Qaeda built into printer cartridges and shipped to the US on cargo planes in 2010.
Both of those bombs used a powerful industrial explosive. Both were nearly successful.
The operation is an intelligence victory for the US and a reminder of al-Qaeda's ambitions, despite the death of bin Laden and other senior leaders.
Because of instability in the Yemeni government, the armed group's branch there has gained territory and strength. It has set up so-called "terrorist camps" and, in some areas, even operates as a de facto government.
But along with the gains there also have been losses. The group has suffered significant setbacks as the CIA and the US military focus more on Yemen.
On Sunday, Fahd al-Quso, a senior al-Qaeda leader, was hit by a missile as he stepped out of his vehicle along with another operative in the southern Shabwa province of Yemen.
Al-Quso, 37, was on the FBI's most wanted list, with a $5m reward for information leading to his capture. He was indicted in the US for his role in the 2000 bombing of the USS Cole in the harbour of Aden, Yemen, in which 17 American sailors were killed and 39 injured.
Al-Quso was believed to have replaced Anwar al-Awlaki as the group's head of external operations.