People scan sheets of paper with preliminary election results in the Harare surburb of Mbare on Sunday.
Zimbabwe's main opposition party is claiming an early lead in elections amid a warning from a government spokesman that declaring victory prematurely would amount to an attempted coup.
"It's a coup d'état, and we all know how coups are handled," government press secretary George Charamba told the state-owned Sunday Mail after the main opposition party, Movement for Democratic Change (MDC), told observers that early results showed it was headed for victory.
MDC, led by former trade unionist Morgan Tsvangirai, said it's leading the race against President Robert Mugabe with 67 per cent of the votes. Its assessment is based on returns from about one-third of polling stations.
The party's secretary-general, Tendai Biti, said MDC won nearly all parliament seats in the main cities of Harare and Bulawayo as well as in some traditional ruling party strongholds.
"This far, short of a miracle, we have won this election beyond any reasonable doubt. We have won this election," Biti told a news conference early Sunday.
Preliminary results were expected by Monday. Final official result may not be known until later in the week, according to election officials.
If no candidate wins more than 51 per cent of the vote, the election will go into a second round.
Meanwhile, MDC said it's investigating reports of vote rigging by the ruling ZANU-PF party to give Mugabe a sixth term in office.
Observers say the official rolls in some districts were inflated with a large number of phantom voters. Opposition reports suggest that hundreds and possibly thousands of Mugabe's opponents were turned away at the polls.
The election has presented Mugabe, 84, with the toughest political challenge to his 28-year rule, badly tarnished in recent years with an economic collapse that has seen inflation rise above 100,000 per cent and unemployment running at 80 per cent.
People in the once-prosperous south African nation, led by Mugabe since its independence in 1980, are also coping with chronic shortages of food, medicine and fuel.
Mugabe repeatedly dismisses his opponents as stooges of former colonial power Britain and accuses the West of sabotaging Zimbabwe's economy.
While visiting Jerusalem on Sunday, U.S. Secretary of State Condoleezza Rice said "the Mugabe regime is a disgrace to the people of Zimbabwe and a disgrace to southern Africa and to the continent of Africa as whole."