Russian officials said the arrest was a "provocation".
Russian national held in Norway for suspected spying
A Russian national has been arrested in Norway on suspicion of spying after he attended a conference on strengthening co-operation between Europe's parliamentary administrations, his lawyer said on Monday.
Russia has strongly denied the charges and demanded the release of the 51-year-old man.
Lawyer Hege Aakre told the Norwegian news agency NTB that her client, who was not identified, was being questioned by Norway's domestic intelligence agency, PST.
The man was arrested on Friday during the European Centre for Parliamentary Research and Documentation event, held at Norway's Parliament, and placed on pre-trial detention for two weeks the following day. No further details were available.
Ms Aakre said her client denies any wrongdoing.
The Russian Foreign Ministry said it had summoned the Norwegian ambassador on Monday to protest the detention it described as a "provocation."
It said that the Russian citizen, whom it identified by his last name and initials, MA Bochkarev, was an official with the upper house of Russian parliament who was attending a seminar organised by the Norwegian parliament.
The ministry denounced the accusations as "absurd" and demanded his immediate release. It lamented what it called "a wave of spy mania around Russia" and warned that "such steps will entail consequences."
Prime Minister Erna Solberg said the case wasn't political, telling NTB from New York, where she is attending a meeting with the United Nations, that the case was "a police matter that is being investigated."
Norwegian media reported that the man is a senior IT adviser with the Russian parliament. They reported that his behaviour at the two-day conference prompted parliamentary officials to contact the intelligence service.