A new agreement allowing Zimbabwe to sell its controversial diamonds was met with caution Friday by rights groups who have documented workplace safety violations and killings in the country's diamond mines.

Miners dig for diamonds in Marange, eastern Zimbabwe. Human rights groups are cautious over a deal to allow Zimbabwe to sell diamonds on the world market. (Tsvangirayi Mukwazhi/Associated Press) Global Witness and Partnership Africa Canada said in a release they welcome the agreement's condition that Zimbabwe make "measurable improvements" in its diamond-mining practices if it wants to sell more than the two batches allowed by Thursday's agreement.

But the rights groups called for more controls in the months ahead. They said the deal averted a crisis over international sales of Zimbabwean diamonds but the "biggest test" of the credibility of the agreement still lay ahead.

"The ball is now in Zimbabwe's court to make good on its promises and act to end one of the most egregious cases of diamond-related violence for many years," said Annie Dunnebacke of Global Witness.

A last-minute deal at a meeting of the Kimberley Process certification scheme in Russia authorized Zimbabwe to sell two batches of diamonds under strict monitoring and regulation through Sept. 1.

Dunnebacke said violations and disputes over Zimbabwe had battered the integrity of Kimberley certification scheme comprising 75 national, industry and lobby groups.

'The system needs urgent and far-reaching reform at a time when consumers are demanding action on blood diamonds.'—Nadim Kara, Partnership Africa Canada

"Ultimately, the success or otherwise of this agreement will be determined by what the main players do next. We fervently hope that the governments in the Kimberley Process will, for their part, hold Zimbabwe to its commitments," she said.

Nadim Kara of Partnership Africa Canada described the agreement as "far from perfect."

"The crisis in Zimbabwe's diamond sector should act as a wakeup call to governments and the diamond industry. ... The system needs urgent and far-reaching reform at a time when consumers are demanding action on blood diamonds," Kara said.

President Robert Mugabe inspects the guard of honour during the opening ceremony of the Parliament in Harare on Tuesday. Mugabe announced that Zimbabwe would go ahead to sell diamonds it is currently mining. (Tsvangirayi Mukwazhi/Associated Press) Mining experts estimate that Zimbabwe's diamond fields, sealed off by police and troops in the districts of Marange and Chiadzwa near the eastern city of Mutare after a diamond rush began in 2006, are likely the biggest deposits found in Africa since the Kimberley fields were discovered in neighbouring South Africa a century ago.

The Mines Ministry says it already has about $1.7 billion of diamonds in storage ready to be sold. Zimbabwe's total international debt is estimated at around $5.5 billion.

The ministry, controlled by President Robert Mugabe's party in the coalition with Prime Minister Morgan Tsvangirai, the former opposition leader, denies wrongdoing and accuses human rights groups of "peddling falsehoods" over rights violations and top-level corruption by politicians and police and military chiefs.

Finance Minister Tendai Biti reported in a budget review statement Wednesday at least $30 million US in recent diamond sales was known to have gone missing and did not end up in state coffers.

Criticism by Western countries and human rights groups deadlocked a Kimberley Process meeting in Israel last month that sought approval for the sales after a regional monitor of the control body reported Zimbabwe had met minimum international diamond mining standards.