OSLO (AFP) - Norway's security police tricked a suspected terrorist cell arrested this week by swapping bomb-making material with harmless liquid, a Norwegian newspaper reported Friday.

• Three Al Qaeda suspects held in Norway
• Central Oslo cordoned off over suspicious bag

Three men arrested in Oslo and Germany Thursday had at the end of 2009 and the beginning of this year each tried to purchase material needed to make several bombs, the VG tabloid reported.

When they began ordering hydrogen peroxide at pharmacies in Norway, the country's Police Security Service (PST) which had them under surveillance swapped the chemical with a harmless liquid, the paper said.

The report came a day after the PST announced the arrest of three men based in Norway who were believed to have ties to Al-Qaeda and were suspected of plotting a terror attack.

The PST, which did not divulge anything about the suspected plot or whether the men were suspected of trying to make a bomb, insisted Thursday it had "had sufficient control of these individuals (leading up to the arrests), and according to our assessment the public have not been in any danger."

The agency identified the suspects only as a 39-year-old Chinese Uighur who had become a Norwegian citizen three years ago, along with a 31-year-old Uzbek national and a 37-year-old Iraqi Kurd, both with legal resident permits in Norway.

VG on Friday however said it had received information that the Iraqi Kurd, who was arrested in Germany, was Shawan Sadek Saeed Bujak, while the man from Uzbekistan was identified as David Jakobsen.

No name was given for the Norwegian citizen arrested, who other media reported was the leader of the group.

The PST would not say what the target of the suspected terrorist plot had been or where it had been set to take place.

Norwegian media however speculated that the traditionally tranquil Scandinavian country may have been the target, perhaps due to its participation in the NATO-led forces in Afghanistan.

Norwegian Prime Minister Jens Stoltenberg, who cut short his holiday to discuss the arrests, described Thursday's events as "the most serious arrests of this kind that have ever been made in Norway."

"Norway is still one of the world's safest countries," he insisted, but cautioned that "we are seeing developments in Norway that resemble conditions in countries where acts of terror have taken place ... We have to be on our guard."