HARARE, Zimbabwe — The first solid evidence of ballot rigging in Zimbabwe’s presidential election emerged yesterday when a senior policeman told the Daily Telegraph that officers marked extra votes for President Mugabe.

Almost two weeks after polling day, the official result has still not been announced. Independent monitors say that the leader of the opposition Movement for Democratic Change, Morgan Tsvangirai, came first.

But the regime’s critics believe that the Electoral Commission — chaired by a judge and close ally of the president, George Chiweshe, — will announce that Mr. Mugabe is leading, although probably falling below the 50% margin needed to avoid a second round.

The MDC said yesterday night that it would boycott a run-off in the presidential poll if one was declared, adding that Mr. Tsvangirai won with a share “much higher” than the 50.3% it claimed last week.

The police officer, who cannot be identified for fear of reprisals, saw a number of ballot boxes carried into a room at police headquarters in Harare last weekend, seven days after the election.

Five or six new recruits from Morris Depot, all in uniform, then filled out extra votes for Mr. Mugabe. Ballots for Mr. Tsvangirai were removed, the officer added, to bolster the president’s share of the vote.

“We were in the corridor and saw the ballot boxes being taken into Room 96,” the officer said. The police headquaters is only about 300 yards from Mr. Mugabe’s office in Harare. “We asked somebody who went in there and saw the trainees filling out the ballot papers. I am not the only one who knows this, there are others. The recruits will do anything they are asked to do. They were all desperate for jobs. If they have to beat people they will do that.”