Thankful Musukutwa, the secretary-general of Zimbabwe's Mines Ministry appeared Tuesday before the Parliament's Committee on Mines, Voice of America reported.

The committee is probing the business practises conducted by the firms developing the controversial Marange diamond field, where grave human rights abuses are suspected.

The Mine Ministry and at least two of the companies summoned by the committee have refused to appear before it, prompting it to say that it would issue court orders compelling them to appear.

Musukutwa testified in a closed-door session, prompting Human Rights Watch Senior Research Dewa Mavhinga to warn that the committee's work would be compromised if its hearings were held in camera.