Harare/Johannesburg - Political tensions in Zimbabwe heightened Tuesday as President Robert Mugabe's government claimed that a "terrorist assassination attempt" had been made on a notorious top officer of the security forces.

The state-controlled daily Herald newspaper said Air Marshal Perence Shiri, commander of the Zimbabwe Air Force, was ambushed by unidentified gunmen as he was driving to his farm in the Bindura district about 80 kilometres north of Harare on Saturday night. It said he suffered a gunshot wound in the palm of his hand.

"The attack on (the) Air Marshal appears to be part of a build-up of terror attacks targeting high-profile persons, government officials, government establishments and public transportation systems," Home Affairs Minister Kembo Mohadi was quoted as saying.

Shiri was in charge of the notorious North Korean-trained Fifth Brigade of the Zimbabwe army held responsible for the bulk of the massacres of an estimated 20,000 civilians during a low-level insurgency in the western provinces of Matabeleland between 1983 and 1987.

On Monday, Harare accused the government of Botswana, its western neighbour, of plotting Mugabe's overthrow with pro-democracy leader Morgan Tsvangirai's Movement for Democratic Change, and of providing "material and logistical support ... for the recruitment and military training of youths for the destabilization of the country ... to effect illegal regime change."

Monday's allegation was denied by Botswana and the MDC, who described the charge "as a dog's breakfast." MDC secretary-general Tendai Biti said that Mugabe's regime was using the conspiracy claim to build up to a declaration of a state of emergency.

MDC officials say members of a group of 15 MDC members being detained since early November have been tortured into confessing they received military training.

The Herald Tuesday cited as evidence of "the buildup of terror attacks" three bomb blasts in police offices in Harare since August and the bombing of a railway line and railway bridge in August. Damage was reportedly slight and no-one was injured.

There has been no reports of attacks on other "high-profile" officials. However, there has been widespread speculation over the death last week of Elliot Manyika, the political commissar of Mugabe's Zanu-PF party, who was killed when his vehicle crashed after a burst tyre. The regime has described the incident as an accident. Manyika was regarded as the key organizer of the party's campaigns of violence against the opposition in recent years.

The regime has carried out no prosecution for the Matabeleland massacres. After the bloodletting, Shiri was promoted to deputy head of the air force, later becoming chief.

On Monday, United Nations secretary general Ban Ki-Moon, in an address to the UN Security Council, said the United Nations attempt to mediate in Zimbabwe had been rebuffed by Mugabe and former South African president Thabo Mbeki, who is mediating in talks between Mugabe's Zanu-PF and the MDC.

The talks to form a unity government have gained added urgency as Zimbabweans continue to succumb in high numbers to cholera, days after Mugabe declared the epidemic had been "arrested."

The death toll in the outbreak that began in August when water and sewerage systems in urban areas collapsed now stands at 978 dead and 18,413 reported cases of infection. (dpa)