Four members of staff were also arrested during a late night raid by security forces on the offices of opposition daily Rai Al Shaab.
Couple arrested in December after holding an engagement ceremony face up to 14 years in prison.
Unity government urged to end all malicious prosecutions of people exercising their rights to freedom of expression after the acquittal of Roy Bennett, a critic of President Mugabe.
Amnesty International has urged the Zimbabwe police to end their intimidation of activists and stop preventing them from exercising their right to peaceful assembly.
It is feared that the young men, who disappeared from Swift Operation Squad detention in Port Harcourt a year ago, were extrajudicially executed.
Members of human rights organization Social Action were stopped and detained earlier this month after leaving their office.
Artist Owen Maseko was arrested after participating in a show depicting atrocities that took place in the Matabeleland region in the 1980s.
An increase in harassment, arbitrary arrests, detentions, torture and other ill-treatment by security forces is anticipated ahead of April's elections.
Amnesty International has called on the Gambian government to immediately charge or release all former government officials detained during a wave of arrests over the past week.