"Ivan is not called one of the best journalists in the country for nothing. We know not only his exceptional professionalism but his character as well. Ivan is a true patriot of Russia, who wrote about the military and space because he was concerned about them. High treason accusation against him looks absurd," the publishing house said.
On Tuesday, investigators asked the court to arrest Safronov over high treason accusations.
He has most recently been working as an adviser to the head of the Russian space agency. According to the Federal Security Service, he is suspected of giving a NATO special service some classified information on defence.
Roscosmos has said that Safronov's detention is unrelated to his work for the space agency.
Dmitry Peskov, the spokesman for the Kremlin, said that the detention of Safronov did not appear to be connected to his work as a journalist.
