Raymond Lidal's exact whereabouts are still unknown.
The freelance journalist had lived and studied Arabic in the capital, mainly writing stories for Norwegian media outlets including the state broadcaster NRK and Bergens Tidende newspaper.
Local witnesses said Lidal was arrested after being caught taking photos of Saudi-led coalition airstrikes from his home in the Old City of Sanaa.
At the beginning of the air campaign, Lidal sent Facebook messages to his friends and colleagues asking advice on how to stay safe under bombardment. He said that he was worried that the majority of the "blasts" he was hearing were from anti-aircraft guns near his home in a residential area.
"I lack any understanding/experience with anything that's got to do with warfare. I didn't even go through our obligatory year in the army," he said on Facebook.
On Thursday, a local Norwegian newspaper published an interview conducted with Lidal two days before he was arrested. In it, the journalist and student said the Yemeni authorities "don't really like journalists without the proper papers." And that: "Officially I'm here as a student."
Lidal first visited Yemen in 2010, returning in 2012 before turning to journalism to fund his Arabic and academic studies, colleagues and friends of Lidal's told CNN.
His use of a student visa was a common practice in the small community of international journalists in Yemen, to circumnavigate the labyrinth of the country's bureaucracy, according to local expats and colleagues of Lidal.
Lidal's family was able to exchange a few words with him on Thursday, associates in Yemen told CNN. Lidal reportedly confirmed he was being held in Sanaa, had not been moved from the capital and was in good health, they said.
Lidal's family remains concerned for his health since he suffers from diabetes, sources close to the case told CNN. A former Arabic teacher described him as a "diligent student" with a good command of the local Sanaa dialect of Arabic.
A spokesman for the Norwegian foreign ministry declined to comment on the specific details of their attempts to contact their citizen, but did say that:
"In our contacts with the authorities in Yemen, we have made it clear that they bear the full responsibility for the life and health of the Norwegian citizen in question as long as he is in their custody."