British official: 'necessary to take action' now against 12 men suspected in terror plot

British authorities rounded up 12 men Monday morning suspected in a terror plot. Police said the arrests are not connected to the Dec. 11 suicide bombing in Sweden.

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British authorities arrested 12 men of Pakistani descent early Monday morning in what was described as a major operation to disrupt a terror plot.

The men are being held on suspicion of the “commission, preparation, or instigation, of an act of terrorism in the UK,” according to the police. The arrest comes after a suicide bombing in Sweden on Dec. 11, Germany's warning on Nov. 17 of "concrete indications" of a series of looming attacks, and travel alerts in October from the US and Japan of terror threats across Europe.

Britain’s terror level threat is currently “severe,” the second-highest rating, which warns of a high likelihood of attack. Today's arrests were carried out by unarmed officers, which the Associated Press said suggested that police did not believe an attack was imminent from the men aged between 17 and 28.

"This is a large-scale, preplanned, and intelligence-led operation involving several forces," said John Yates, Britain’s top counterterrorism police official, reports Agence France-Presse. "The operation is in its early stages so we are unable to go into detail at this time about the suspected offences. However, I believe it was necessary at this time to take action in order to ensure public safety."

Except for one suspect who was arrested in Birmingham, they were arrested at their homes in Cardiff, Stoke-on-Trent, and London around 5 a.m., and police are now searching their homes.

Counterterrorism sources told the BBC that the “significant” operation was related to an investigation into “Al-Qaeda-inspired terrorism.” The BBC reports that the plot was related to explosives, and did not contain a plan for a Mumbai-style killing spree by coordinated gunmen.

In September, European security officials warned that a group was planning such attacks in the UK, Germany, and France. The Christian Science Monitor reported at the time that such an attack was likely far from being realized.

The BBC also reports that the sources do not believe the plot is linked to last week’s bombing in Stockholm by an Iraqi-born man who had lived in Britain. Nor was the plot part of a coordinated series of holiday season attacks, according to a British security official quoted by the Associated Press. Iraqi officials warned last week that captured insurgents said the bombing in Sweden was a part of a series of planned attacks on Europe and the US.

CNN reports that Britain’s intelligence organization, MI5, led the operation, and says that the suspects were all of Pakistani descent. The BBC and the Guardian said some of the suspects were from Bangladesh.

European nations have in recent months issued warnings of possible plots. Beginning with a vague “travel alert” from the US State Department in October telling travelers to Europe to be advised of possible terror attacks, several European nations joined with warnings of their own. As the Monitor reported, France’s warning focused specifically on Britain, saying an attack there was “very likely.”

Today's arrests were the first major raid in Britain since April 2009, when 12 suspects were arrested in one day. Police at that time claimed to have broken up a plot to attack Manchester, but the suspects were never charged, according to the Associated Press.