The Norwegian Parliament said on Wednesday it had sustained a fresh cyber attack, six months after a previous one was publicised.
"We know that data has been extracted but we do not yet have a complete overview of the situation," parliament's administrative chief Marianne Andreassen said in a statement.
The attack was linked to a "vulnerability" in Microsoft's Exchange software, parliament said.
"Parliament does not know who is behind the attack," it said.
The previously publicised attack, in September, was launched by Russia, Norwegian foreign minister Ine Eriksen Soereide said in October, an accusation Moscow denies.