Zimbabwe's prime minister, who is also the country's opposition leader, has said that it has lost faith in the electoral commission after "chaotic and disorganised" special voting for security forces ahead of key polls.
Long queues and the late delivery of ballot papers marked the two-day early vote, which started on Sunday for police officers and soldiers who will be on duty on July 31 when the rest of the country votes.
Many security force agents found themselves unable to vote, drawing condemnation from Tsvangirai's Movement for Democratic Change (MDC) on Tuesday.
"The process is chaotic and disorganised and has exposed ZEC (Zimbabwe Electoral Commission) as a body not ready to the task," MDC secretary general Tendai Biti told a news conference.
In just over a fortnight, presidential and parliamentary polls pit incumbent President Robert Mugabe against his arch-rival Tsvangirai, 61.
Mugabe, 89, hopes to extend his 33-year-rule in the vote that will end the pair's unity government formed after deadly disputed polls in 2008.
On Tuesday, police officers waited at the city hall in the capital Harare, hoping to cast their votes even though polls closed Monday night.
Presiding officers had been deployed late at most polling stations and MDC polling agents were chased away in eastern province Manicaland, said Biti.
"It's a clear breach of the laws of Zimbabwe," Biti added.
"We are really worried with (the) ZEC and have lost institutional trust in them. The junta has taken over and ZEC is no longer in charge."
The MDC in the past has complained that former security force members - traditionally loyal to Mugabe - served on the ZEC.
The commission's former head, George Chiweshe, used to be a brigadier general in the army.
Reports of rights abuses and intimidation of political opponents have implicated the security forces, which fall under Mugabe's control.
On Friday, rights group, Amnesty International also raised concerns about increasing intimidation against human rights defenders. The group said:
"The clampdown on the work of human rights defenders is a worrying indicator that government agencies remain actively hostile to civil society,” said Noel Kututwa, Amnesty International’s Africa Deputy Programme Director.