Police in Austria have arrested two people suspected of having links to the Paris attacks at a refugee shelter in Salzburg, prosecutors say.
Robert Holzleitner, from the state prosecutor's office, told the BBC the pair had arrived from the Middle East.
They were arrested on suspicion of belonging to a terrorist organisation.
An unconfirmed report said the men had travelled with members of the terror cell that carried out the 13 November attacks that killed 130 people.
The mass-circulation Kronen Zeitung (KZ) claimed the suspects were French. It said they had entered Europe via Greece with Islamic State (IS) militants who later carried out the Paris attacks, using forged Syrian passports.
The detained men were said to have been awaiting orders for new attacks, when they were arrested at a migrants' shelter in Salzburg over the weekend.
The Kronen Zeitung's report has not been independently verified but other reports said the threat was being taken very seriously.
Two other men were said to have been arrested at the same camp two weeks ago on suspicion of being IS militants.
Justice ministry official Christian Pilnacek played down suggestions that two men, who were detained at the weekend, had been planning an attack. "Terror is too strong a word for that," he told Austrian radio.
"We are investigating possible membership of a terrorist organisation. Like so often, it is a puzzle that has to be put together piece by piece."
Mr Pilnacek also warned against conflating the terror threat in Europe with the migrant crisis.
"Refugees shouldn't come under general suspicion - that would not be appropriate," he stressed, adding that because of the heated nature of debate, the judiciary would only make firm information public.
The Kronen-Zeitung said the two men arrested men had Algerian and Pakistani roots. It did not give details of its sources.
The news of the Austrian arrests came as Belgium's justice minister revealed that police may have missed opportunities to arrest fugitive suspect Salah Abdeslam two days after the Paris attacks.
In comments to be broadcast by television station VTM, Koen Geens said security forces had information that Abdeslam was possibly staying in a house in Molenbeek on 15 November. The Brussels neighbourhood has come under the spotlight over its links to a number of jihadist suspects.
However, police could not raid the building until the morning of 16 November due to laws banning such searches between 21:00 and 05:00, Mr Geens was quoted as saying by Dutch language daily Het Laatste Nieuws.
He also described the fact Abdeslam had not been picked up at the border crossing between France and Belgium the day after the attacks, despite being on a list of suspects, as "bad luck" due to the timing.
Investigators say Abdeslam may have driven the suicide bombers at the Stade de France to their target on the night of the Paris attacks.
But his precise role remains unclear. There are suggestions he was meant to carry out a suicide attack but decided against it.
The assaults left 130 people dead and more than 350 wounded.