Zimbabwe's High Court on Thursday backed Chief Justice Luke Malaba's right to resume work despite a previous ruling that the president's decision to extend Malaba's tenure breached the constitution because he has turned 70.

The Malaba case has become the focus of a tussle between the High Court and President Emmerson Mnangagwa, who introduced a constitutional amendment that raised the retirement of Constitutional and Supreme Court judges to 75 from 70.

Lawyers have challenged the amendment but Malaba has resumed his work, prompting one of the lawyers to file contempt of court charges against the chief justice.

However three High Court judges rejected the contempt of court charges on Thursday without immediately giving a reason for their verdict.