Published: Jul 08, 2010 11:50 AM EDT
Updated: Jul 08, 2010 8:52 AM EDT

OSLO (AP) - Three suspected al-Qaida members were arrested

Thursday morning in what Norwegian and U.S. officials said was a

terrorist plot linked to similar plans in New York and England.

The three men, whose names were not released, had been under

surveillance for more than a year. Officials believe they were

planning attacks with portable but powerful bombs like the ones at

the heart of last year's thwarted suicide attack in the New York

City subway.

U.S. Attorney General Eric Holder has called that one of the

most serious terrorist plots since 9/11. On Wednesday, prosecutors

revealed the existence of a related plot in Manchester, England.

Officials believe the Norway plan was organized by Salah al-Somali,

al-Qaida's former chief of external operations, the man in charge

of plotting attacks worldwide.

The officials spoke on condition of anonymity because they were

not authorized to discuss the case. The Norwegian Police Security

Service said only that the three were arrested on suspicion of

"preparing terror activities."

Al-Somali, who was killed in a CIA drone airstrike last year,

has been identified in U.S. court documents as one of the

masterminds of the New York subway plot. Two men have pleaded

guilty in that case, admitting they planned to detonate explosives

during rush hour. A third man awaits trial.

A news conference was planned for later Thursday.

Officials said it was not clear the men had selected a target

for the attacks but they were attempting to make peroxide bombs,

the powerful homemade explosives that prosecutors say were

attempted in both New York and England.

U.S. and Norwegian counterterrorism officials worked closely

together to unravel the Norwegian plot, officials said. Janne

Kristiansen, the head of the Police Security Service, traveled to

the U.S. this spring to discuss some of the closely held

intelligence that been gathered in the case.

In Washington, Justice Department spokesman Dean Boyd had no

comment.

Officials did not say why Norway was a target, but al-Qaida No.

2 Ayman al-Zawahri has called for attacks on Norway, among other

countries.

Magnus Norell, a terrorism expert at the Swedish Defense

Research Agency, said Norway's 500 troops in Afghanistan could be a

factor, as could the 2006 controversy sparked by a Danish

newspaper's publication of 12 cartoons depicting the Prophet

Muhammad.

Norell said the controversy has extended to neighboring Norway

and Sweden after newspapers there republished the cartoons and

later published similar cartoons. Images of Muhammad, even

favorable ones, are considered blasphemous by many Muslims.