Amnesty International on Friday called on Zimbabwean authorities to refrain from manipulating the country's laws to harass human rights activists and opponents of veteran President Robert Mugabe.

"The continuation of human rights violations against critics of President Robert Mugabe's ZANU-PF party cast doubt on whether the country will be able to hold an election free from violence and human rights abuses similar to the 2008 second round of the presidential election," the group said in a statement.

Amnesty urged Mugabe to "rein in elements in the security forces who seek to undermine the (government of national unity) by ordering arbitrary arrests and unlawful detention of his perceived opponents."

Mugabe formed a powersharing government with Prime Minister Morgan Tsvangirai in 2009 to avoid a tip into full-fledged conflict in the aftermath of a presidential run-off which Tsvangirai boycotted in protest at deadly attacks on his supporters.

Despite the unity government, rights activists are frequently arrested or harassed in the course of their work.

"The government should unconditionally drop all the charges against people arrested solely for their work as human rights defenders or for their association with political parties of their choice," Amnesty said.

The statement came after a court placed three activists from local media advocacy group Media Monitoring Project Zimbabwe on remand on charges of undermining or insulting Mugabe.

In another case this week, a court acquitted Joel Hita of the Zimbabwe Human Rights Association who had been charged under a security law for a holding a photo exhibit on the 2008 polls.

Activists Jenni Williams and Magodonga Mahlangu of Women of Zimbabwe Arise face charges of kidnapping a witness to a September protest that was violently dispersed by police.

Two booksellers were detained last weekend for selling copies of Tsvangirai's biography. - ANP/AFP