The Cumhuriyet newspaper's editor-in-chief Can Dundar and Ankara bureau chief Erdem Gul have been detained since November over a report alleging that President Recep Tayyip Erdogan's government tried to ship arms to Islamists in Syria.
They had been due to go on trial on March 25 and had so far been held in jail for 92 days.
The constitutional court, which convened to discuss the journalists' individual petitions, yesterday ruled that their "rights to personal liberty and security had been violated," the court said in a statement on its website.
The decision was overwhelmingly approved with 12 votes for and three against, Turkish media reports said.
The case has now been sent back to the lower criminal court which should rubber-stamp the top court's decision and thus allow the release of the journalists possibly within hours, the private NTV television station reported.
Reports said their lawyers had already filed the petition for the pair's release at the Istanbul court which ordered their arrest.
Since then, they have both been held in the Silivri jail on the outskirts of Istanbul.
They have been formally charged with obtaining and revealing state secrets "for espionage purposes" and seeking to "violently" overthrow the Turkish government as well as aiding an "armed terrorist organisation."
Both Erdogan and the head of the National Intelligence Organisation (MIT) Hakan Fidan -- the president's hugely powerful but low-profile ally -- are named as plaintiffs in the 473-page indictment.
Press freedom group Reporters Without Borders (RSF) said it was "delighted" by the decision for the journalists expected release but warned they still faced trial.
