HARARE, Zimbabwe — Zimbabweans lined up for hours Saturday to vote in elections that present President Robert Mugabe with his toughest political challenge in 28 years in power.

Voting was generally reported as peaceful but were some complaints of irregularities and minor violence.

The opposition accuses Mugabe of plotting to steal the election. Mugabe told reporters he would accept whatever results emerged and rejected the charges that he had already orchestrated his own victory.

"We don't rig elections," he said.

The economic collapse of Zimbabwe, once the region's breadbasket, has dominated the campaign. The opposition accuses Mugabe of misrule and dictatorship. Mugabe, appealing to national pride, blames the West — and charges his opponents as being stooges for former colonial ruler Britain.

In southern Bulawayo, an opposition stronghold, 78-year-old Moffat Simon Mabhena was among many who lined up to vote hours before the scheduled 7 a.m. poll opening.

"The message is very clear: We want to see change in this country," Mabhena said. "I have been here since 2:30 a.m. and it's because I want to see Robert Mugabe out."

A parliamentary candidate for Mugabe's party in Bulawayo, Judith Mkwanda, reported two explosions outside her home just after midnight. Later Saturday, several window panes in her home could be seen shattered. No injuries were reported.

Mkwanda said she had heard passers-by shouting insults at Mugabe and members of the ruling ZANU-PF party the night before, and believed she was targeted "just because I am a ZANU-PF member."

Running against Mugabe are opposition leader Morgan Tsvangirai, 55, who narrowly lost disputed 2002 elections, and former ruling party loyalist and finance minister Simba Makoni, 58. Makoni threatens to take votes from both the opposition and the ruling party.

Zimbabweans are voting in a single day for the first time for president, 210 legislators, 60 senators and 1,600 local councilors. Preliminary results are expected by Monday.

All three presidential candidates voted early Saturday.

Tsvangirai sounded a resolute note: "The people's victory is assured."

The independent Zimbabwe Election Support Network's monitors reported a heavy police presence at polling stations, ostensibly to help illiterate voters and allowed under a belated presidential decree that breaks an agreement signed with the opposition. Some fear it could frighten away opposition voters.

Tendai Biti, a senior official in Tsvangirai's party, told reporters that his party's agents reported 200 voters — more than half of those who had cast votes in that polling place — were assisted by police in an area where the illiteracy rate was closer to 10 percent.

Biti said his party's agents had been barred from polling stations in several districts. The party also was investigating a report that six stuffed ballot boxes were found before voting got under way in one district, Biti said.

There are 9,000 polling stations for 5.9 million voters, though that number that has been disputed. Independent democracy watchdogs have complained there were too few stations in urban opposition strongholds, and that they have seen the names of dead or fictitious people on the official voters' list.

An observer from the Pan-African Parliament said the longest queues in Harare were at two polling stations on the edge of a vacant plot where 8,450 people had registered as residents.

The observer, who spoke on condition of anonymity because he was not authorized to speak to the media, gave an Associated Press reporter a letter to the Zimbabwe Electoral Commission asking for an explanation.

State Department spokesman Sean McCormack said Friday, "There are a lot of big question marks hanging over this election in terms of the integrity of the electoral process."

Friday night, monitors from the 14-nation Southern African Development Community said they had observed "a number of matters of concern," which they did not identify.

Zimbabwe has barred observers traveling from the United States and the European Union, but the State Department said 10 people from its embassy in Harare were monitoring the elections.

After independent monitors said 2002 elections were rigged, Western nations imposed visa bans and froze bank accounts for Mugabe and 100 of his cronies, but Mugabe has convinced many supporters that those limited sanctions are to blame for the country's woes.

Mugabe's critics say it was the government-ordered, often violent eviction of white farmers to hand land over to blacks that doomed the agriculture-based economy.

In a southern African country that once exported food, tobacco and minerals, Zimbabweans struggle to survive inflation in excess of 100,000 percent, crippling shortages of food, water, electricity, fuel and medicine.

A third of Zimbabwe's population, or an estimated 5 million people, are political and economic refugees. With no provisions for overseas voting, some were participating in a mock online election. In London, the Zimbabwe Vigil group was holding elections in front of the Zimbabwe Embassy for frustrated refugees.