The men hoped to kill as many people as possible at Jyllands-Posten within 20 minutes, recordings made by the Danish security service PET and published Monday in the Ekstra Bladet newspaper show.
The three men traveled from Sweden to Denmark Dec. 29 and met near Copenhagen to plot the attack, authorities said.
During a prayer, one of them said, "When the unfaithful are gathered, tie them up and cut their throats," the report said.
They were later arrested and PET found automatic weapons, silencers and heavy tape in the apartment.
Last Thursday, a Danish court ruled Munir Awad, Omar Abdalla Aboelazm and Mounir Dhahri should stay in solitary.
A Swedish court Monday continued the jailing of Sahbi Zalouti, who was arrested in Stockholm, the Swedish news agency TT reported.
All four men deny planning any terrorist acts.
In 2005, Jyllands-Posten published cartoons of the Prophet Mohammed, sparking riots across the Muslim world. Extremists offered rewards for killing the cartoonists.