Zimbabwe's upcoming general elections will take place amid a crackdown by the state on human rights activists and opposition supporters, Amnesty International warned in a report released on Friday.

The London-based human rights group said there was a "systematic clampdown" on free speech and the right to assemble.

While violence in the run-up to the July 31 poll has been lower than in previous election cycles, campaigners for a free vote are being subject to intimidation.

Earlier this month, police detained four members of a pro-democracy group in the eastern border town of Mutare for two nights because they were distributing T-shirts and encouraging Zimbabweans to go and register for participation in the elections.

Zimabweans paved the way for the elections by approving a new constitution in a March referendum

They will stand trial on August 1, 2013 to answer charges of conducting voter education without authority from the Zimbabwe Electoral Commission.

Weekend in detention

An aspiring parliamentary deputy for the Movement of Democratic Change (MDC) is spending this weekend (13.07.2013 – 14.07.2013) in police custody on charges of assault. His lawyer Marufu Mandevere told Deutsche Welle his client had never assaulted members of President Robert Mugabe's ZANU-PF party as had been claimed, and he suspected his client had been detained in order to derail his MDC election campaign.

Zimbabwean police officials deny allegations of being partisan. A police spokesman told the German news agency dpa they did not condone "any member of us violating human rights."

A ZANU-PF spokesman told Deutsche Welle that Amnesty International was trying to "tarnish the image" of Zimbabwe.

Partners in an uneasy alliance: Robert Mugabe (left) and Morgan Tsvangirai (right)

Elections in 2008 descended into widespread violence largely targeting the opposition. Some 200 people were killed across the southern African nation, thousands were arrested and many tortured.

Appeal to SADC

Referring to the upcoming elections, Noel Kututwa, Amnesty's Africa deputy programme director, told Deutsche Welle that his rights group "wanted to see SADC as well as the African Union taking a more pro-active stance when it comes to any reports that related to state-sponsored electoral violence."

SADC, the 15-nation Southern African Development Community, brokered the formation of a shaky power-sharing government between President Robert Mugabe and his arch rival Prime Minister Morgan Tsvangirai in 2009. Zimbabweans go to the polls on July 31 to choose a successor to that administration.

"The stakes are high in this election and the run-up to it cannot simply be treated as business as usual, either by stakeholders in Zimbabwe or by the international community," said Kututwa.