Soldiers took to the streets with armored cars and water cannons Friday as Zimbabwe's security chiefs warned that they were ready to confront any violence during the weekend's crucial presidential election in this economically wrecked African nation.

The opposition urged its supporters to defend their ballots against what they have charged is a plot by the ruling party to rig Saturday's vote.

President Robert Mugabe, the 84-year-old revolution leader facing the toughest challenge since he won power in 1980, told his final campaign rally that the election would show Zimbabweans' opposition to former colonizer Britain, which he accuses of supporting the opposition.

"Zimbabweans are making a statement against the meddling British establishment," the president told about 6,000 people in Epworth, an impoverished town outside the capital of Harare.

Mugabe called for discipline at the polls despite "provocation from outsiders who are already claiming the elections are not free and fair."

Running against Mugabe are opposition leader Morgan Tsvangirai, 55, who narrowly lost the disputed 2002 election, and former ruling party loyalist and finance minister Simba Makoni, 58. Preliminary results are not expected until Monday.

Tsvangirai urged opposition supporters to stay at polling stations until they close and counting begins.

"They would not rig in front of you," he told about 4,000 people in Domboshawa, a farming community north of Harare. "We have won this election already. What's left is for us to defend our vote."

Friday night, election monitors from the 14-nation Southern African Development Community said they had observed "a number of matters of concern," which they did not specify. They said they would investigate and raise the issue with relevant authorities.

Zimbabwe's security chiefs are firmly behind Mugabe and they gathered to warn against unrest, telling reporters the armed forces were "up to the task in thwarting all threats to national security."

In Harare, soldiers on all-terrain vehicles and police on motorcycles escorted a convoy of armored cars and water cannons making a show of force.

"Those who have been breathing fire about Kenya-style violence should be warned," the security chiefs said, referring to bloody protests in that East African nation after a December presidential election so rigged no one knows who won. More than 1,000 people were killed there.

The security chiefs have made veiled threats of a coup if Mugabe should lose. The Defense Forces commander, Gen. Constantine Chiwenga, warned that his soldiers would not serve anyone but Mugabe.

On Thursday, Tsvangirai appealed to soldiers and other public servants to reject any attempt to fix the voting. "Mugabe cannot rig elections by himself," he said. "If someone tells you to falsify the results of the elections, ignore the instructions."

Mugabe has said he would crush any anti-government demonstrations.

"Just dare try it," he was quoted as saying by the state-controlled Herald newspaper. "We don't play around while you try to please your British allies. Just try it and you will see."

Mugabe blames Britain and other Western nations for the ruin of this southern African nation's economy, which once exported food, tobacco and minerals. Zimbabweans now struggle to survive amid 100,000 percent inflation and dire shortages of food, water, electricity, fuel and medicine.

Some 5 million people, a third of the population, are thought to have fled the country in recent years. An average of 1,000 Zimbabweans pick their way through barbed wire barriers to sneak into South Africa every day, the Organization of International Migration says.

Western sanctions introduced after independent monitors said the 2002 election was rigged involve visa bans and frozen bank accounts for Mugabe and 100 of his cronies, but the president has convinced many supporters the sanctions are to blame for the country's woes.

Mugabe's critics argue that the agriculture-based economy was derailed by the government-ordered, often violent eviction of white farmers so their lands could be handed over to blacks.

But Fungai Shangwa, a 30-year-old unemployed mother of two, said land reform was one of the reasons she would vote for Mugabe.

"The opposition will give back land to the whites," said Shangwa, who got no land herself. Most of the seized farms went to Mugabe's friends, relatives and allies.

The president also is accused of trying to buy votes by handing out tractors, power generators and state-subsidized food.

Makoni, a longtime ruling party politburo member until he was kicked out for challenging Mugabe in February, has shaken up Zimbabwe's politics with his appeal to disillusioned citizens, threatening to take votes from both the opposition and Mugabe.

Makoni told The Associated Press in an interview on Thursday that his priority as president would be to restore the rule of law to pave the way for economic recovery and re-engage with the international community.

"The cure is not big piles of money," he said. "We will need money to deal with the crises of food, energy and water, but the solution lies in the revival of our own institutions and production in a climate of constitutional order."

Tsvangirai and other opponents have said Mugabe should be tried, possibly at an international human rights court, for abuses such as the massacres of an estimated 30,000 people during a campaign to subjugate the minority Ndebele tribe in the 1980s.

Makoni said he would not mount a witch hunt against Mugabe, but he also said he would give no special immunity to Mugabe.

At a joint news conference Thursday, their first, Makoni and Tsvangirai appealed to election organizers and regional observers to prevent vote rigging.

They complained they had yet to receive full nationwide voter lists. But Makoni said the partial lists showed enough problems to indicate "a very well thought out and sophisticated plan to steal the election from us."