A climate of fear and intimidation means next week's parliamentary elections in Zimbabwe will not be free and fair, Human Rights Watch says.
Food aid is reserved for Zanu-PF supporters, Human Rights Watch says
Its new report finds there is less violence than in previous elections but threats and fear remain widespread.
The group urges southern African election observers, among the few invited, to take this into account when compiling their report.
South Africa's president has said he thinks the elections will be fair.
The report was complied by researcher Tiseke Kasambala who worked with a team in Zimbabwe over several months.
"If Sadc [Southern African Development Community] members fail to take into account abuses in the long run-up to the polls, Sadc's ability to foster democratic change in the region will be compromised," she said.
The 35-page report lists numerous incidents where opposition supporters have been arrested or beaten by ruling Zanu-PF activists with impunity.
The government says the opposition is free to campaign
Traditional chiefs have been asked to compile lists of potential opposition supporters, and voters in desperately hungry rural areas have been told they might not get food aid if they don't vote for the ruling party, Ms Kasambala said.
The report reaches similar findings to one published last week by another human rights group, Amnesty International.
Zimbabwe's ruling Zanu-PF party denies rigging previous elections and says the opposition MDC is crying foul because it is losing support.
The government also points to electoral reforms, such as the setting up of an Electoral Commission and Court.
In the court's first ruling, it allowed jailed MDC MP Roy Bennett to seek re-election.
But President Robert Mugabe described the ruling as "madness" and urged his supporters to ignore it, while also vowing to appeal.
Zimbabwe has been accused of only inviting election observers from groups which backed controversial elections in 2000 and 2002.
The European Union has been banned, along with the Sadc parliamentary forum, which the United Nations news agency, Irin, says was the only African group to say the 2002 presidential poll was not free and fair.
A delegation from South Africa's ruling ANC has been allowed, along with groups from other southern African governments.
Meanwhile, the Zimbabwean, which is produced by exiles and describes itself as the only newspaper available to Zimbabweans internationally, is due to launch online on Monday.