Three people have been arrested in connection with a plot to bomb targets in Norway, police in Oslo have said.
Two of the plotters were arrested in Norway and one in Germany, said the head of the Norwegian security police, Janne Kristiansen.
The men - a Uighur from China, an Iraqi and an Uzbek - are said to have ties to al-Qaeda and to be linked to bomb plots in the US and UK, Ms Kristiansen said.
The three, all Norwegian residents, had been under surveillance for a year.
US prosecutors say the Norwegian case is linked to foiled bomb plots in New York and the English city of Manchester.
"We believe this group has had links to people abroad who can be linked to al-Qaeda, and to people who are involved in investigations in other countries, among others the United States and Britain," Ms Kristiansen said.
She said one of the men was a Norwegian citizen, 39, a Muslim Uighur from China, who had lived in Norway since 1999.
Another was an Iraqi citizen, 37, who was granted Norwegian residency on humanitarian grounds.
The third man was an Uzbek national, 31, who was granted permanent residency in Norway on grounds of family reunification, Ms Kristiansen said.
She gave no details of where the men were arrested, nor any information about locations which may have been targeted for attacks.
Ms Kristiansen said the arrests had been brought forward because news of the probe was about to appear in the international media.
"Such an exposure of the case, without a foregoing arrest, could have proved destructive to the investigation, and with great danger of destruction of evidence," she told a news conference in Oslo.
"We have not chosen this timing completely by ourselves, but we think that we have a solid case, which in the end, naturally, will be up to the courts to decide."
The BBC's security correspondent Gordon Corera says Norway may have been targeted because it has troops in Afghanistan.
On Wednesday, US prosecutors unveiled charges against four men wanted over a plot to bomb the underground system in New York.
They also brought extra charges against a fifth man who is awaiting trial over the alleged conspiracy, foiled last September.
Two other men, Colorado resident Najibullah Zazi and New Yorker Zarein Ahmedzay, have already pleaded guilty.
The US Attorney General, Eric Holder, has described the New York conspiracy as one of the most serious terrorist plots since the 9/11 attacks in 2001.
"The charges reveal that the plot... was directed by senior al-Qaeda leadership in Pakistan," the US Department of Justice said in a statement.
It continues: "[The plot] 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."
One of those named by New York prosecutors is Abid Naseer.
The US is seeking the extradition of the Pakistan-born 24-year-old, who was arrested in the north-east of England on Wednesday.
Mr Naseer was remanded in custody by a court in the UK.
The former construction site worker is suspected of being the ringleader of a plot, thwarted in April 2009, to bomb targets in Manchester city centre.
As in Oslo, the police operation in Manchester had to be brought forward.
Police made arrests ahead of schedule in the Manchester plot after a senior UK police officer unwittingly revealed details of the operation.
A bid to put Mr Naseer on trial in Britain was aborted last year and his deportation was blocked when a judge said he could face torture in Pakistan.