Most of the group are South African

Their lawyer said the High Court in Zimbabwe had granted permission for their case to go to the Supreme Court.

Neither British ex-SAS officer Simon Mann, who was jailed for seven years, nor two pilots will be able to appeal.

The group of 64, nearly all with South African passports, were sent to prison for 12 months for illegally landing at Zimbabwe's main airport.

The authorities said they were en route to Equatorial Guinea to overthrow President Teodoro Obiang Nguema Mbasogo in the oil-rich country.

But they were found guilty of lesser charges of violating immigration and aviation laws.

Charges

Simon Mann was convicted in Zimbabwe of trying to buy weapons in the country en route to carry out the coup.

The two pilots received 16-month sentences.

Sir Mark Thatcher has denied involvement in the plot

In Equatorial Guinea, 14 other people have been found guilty of charges linked to the coup plot, including plot leader Nick du Toit who received 34 years.

Mark Thatcher, the son of the former British prime minister, is also facing legal action in South Africa linked to the alleged plot.

He denies accusations from Equatorial Guinea that he helped finance the operation.

The conduct of the trials in Zimbabwe and Equatorial Guinea were criticised in the West, amid allegations of torture and forced confessions.

Earlier on Thursday, an international group of lawyers criticised Zimbabwe's legal system saying it had ceased to be independent and impartial.