JOHANNESBURG - A Zimbabwe prison officer has used a hidden camera given to him by a British newspaper to film how he and his colleagues were forced to vote for Robert Mugabe in last month's widely criticized presidential runoff.

The Guardian has posted the film on its Web site and says in the film and accompanying stories that the officer, Shepherd Yuda, fled Zimbabwe on Friday and is now with his family in an undisclosed location.

International observers said the June 27 runoff was not free or fair, largely because of violence against opposition supporters.

There also were reports of ballot tampering as described in Yuda's film, with members of the security forces and others not allowed to vote in secret.

Zimbabwean officials have rejected criticism of the election, which opposition Movement for Democratic Change leader Morgan Tsvangirai pulled out of as the only other candidate.

Mugabe was declared winner on June 29 and took the oath of office within hours of the release of results.

The film, which lasts about 10 minutes, shows a senior official identified as a member of Mugabe's party handing out postal ballots to Yuda and other prison workers and watching as they mark them.

It's clear they feel they have no choice but to vote for Mugabe, for fear of what the senior official might do if they vote for the opposition.

Later, in private, Yuda sits in front of the camera and says that marking an `X' on the ballot next to Mugabe's photo "was the most difficult moment of my life."

Other scenes in his film show prison workers speaking fearfully of a colleague's relative being abducted by militant Mugabe supporters, and a meeting at which prison workers are told to vote for Mugabe.

It also shows some famous prisoners, including No. 2 opposition leader Tendai Biti and civil rights activist Jenni Williams. Biti, charged with treason, and Williams, charged in a separate case with disturbing the peace, each have since been released on bail