Biti's lawyer said he is charged with "treason and making malicious statements detrimental to the interests of the state," The New York Times reported.
Police only brought Biti to court when a judge ordered it, CNN said.
Biti was arrested Thursday at the airport in Harare as he returned from a two-month stay in South Africa. The charges involve giving the results of the March election before the official release and discussing plans for government change -- but because the charges were elevated to treason the case has become a capital one.
Also Saturday, MDC presidential candidate Morgan Tsvangirai was detained by police. While he has never been held for longer than a couple of hours, he has been hampered in campaigning.
Zimbabwean President Robert Mugabe warned of possible war Friday if his opponents try to take power in the June 27 presidential election runoff.
Mugabe saiad liberation war veterans were preparing to take up arms if the Movement for Democratic Change wins the presidential runoff, the Times of London reported.