HARARE, March 30 : Zimbabwe's main opposition party on Sunday claimed an early lead in elections, including in a rural stronghold of President Robert Mugabe, in an apparent effort to thwart any attempt to rig the vote count.

The Movement for Democratic Change said party leader Morgan Tsvangirai was leading the presidential race with 67 percent of votes, based on returns from 35 percent of polling stations. With three-quarters of Zimbabwe’s population in rural areas where Mugabe garners most of his support, it was impossible to determine what those figures meant to the race.

Party secretary-general Tendai Biti told a news conference they based their claim on results from Saturday’s balloting posted on the doors of polling stations overnight, which party election agents sent by mobile phone text messages.

Police had tried to persuade the opposition leaders not to announce results, arguing that it was illegal. But the opposition party’s lawyers said the information already was in the public domain.

The announcement defied a stern warning from the southern African nation’s chiefs of security, who already have said they would not tolerate an opposition victory. “We warn anyone of such inclination that we will not tolerate any such (unofficial election result) pronouncements as they have the effect of trying to take the law into their own hands thereby fomenting disorder and mayhem. Everyone is therefore advised to follow the law,” they warned on Friday.

Biti said they had won nearly all parliamentary seats in the two biggest cities, Harare and Bulawayo, which was no surprise as those are opposition strongholds. But he said they also had won in Mashonaland West and Masvingo districts as well as the northeastern town of Bindura, all areas where Mugabe has swept votes in the past.

Bindura, a rural mining and agricultural center, is home to the feared youth brigade of Mugabe’s ruling party—tens of thousands of thugs known for beating up opposition supporters.

“The people’s victory is on course, beyond a shadow of a doubt,” Biti said Saturday night. “We have absolutely no doubt that we are winning this election.”

The elections presented Mugabe with the toughest challenge ever to his 28-year rule. Voting was generally peaceful, with Zimbabweans standing in lines for hours, but African observers questioned thousands of names on the official roll.

The 84-year-old Mugabe, in power nearly three decades, dismissed rigging charges. “I cannot sleep with a clear conscience if there is any cheating,” he said on Saturday after voting and promising to respect results. “If you lose an election and are rejected by the people, it is time to leave politics.”

The Zimbabwe Electoral Commission chairman, Judge George Chiweshe, said, “ We will be releasing the results as soon as we can,” he said. But election observers who visited the commission’s headquarters early on Sunday said it appeared to have only a skeleton staff and appeared in no rush to release results.