Cassimjee Bilal, 28, Henry Hadebe, 57, Samuel Risimati Baloyi, 40 and Sidney Masilo, 40, were hired to deliver trucks which were part of a one-million-dollar deal between Grace Mugabe and her ex-business partner Ping Sung Hsieh, a Taiwanese-born South African.

The men were arrested on arrival in Harare on February 20 and charged with fraud, after a business deal between Ping and the first lady went sour.

"The magistrate issued a warrant of arrest this morning," their lawyer Beatrice Mtetwa told AFP.

"They were supposed to appear in court for trial but they did not turn up at the court. I don't know where they are. They haven't been in touch with me, that's why I couldn't even oppose the issuing of the arrest warrant."

The truck drivers were released on bail after two weeks in prison and ordered to stay at a house in Harare, with strict conditions to report regularly to the police.

It was not clear whether the men were still in Zimbabwe or had skipped the country.

Prosecutors claim the relationship between Grace and Ping dates back to 2007 when funds were transfered from the Reserve Bank of Zimbabwe to one of the businessman's companies for the purchase of trucks.

Two weeks ago a South African court turned down an extradition application by Zimbabwean authorities to have Ping stand trial in Harare for a case related to the cash transfer.