The families of Frik Potgieter and Peter Huxham believe they were jailed because a Cape Town court seized a superyacht and two mansions owned by Equatorial Guinea's vice-president.

The "completely desperate" families of Frik Potgieter and Peter Huxham, two South African engineers held in prison in Equatorial Guinea for more than nine months, have urged the South African government to get them home for Christmas.

Their families say the two men are innocent and were arrested in the Central African country in revenge for a South African court ordering the seizure of a superyacht and two luxury homes in Cape Town owned by the vice-president of Equatorial Guinea, Teodoro "Teodorin" Nguema Obiang Mangue, the playboy son of the president, Teodoro Nguema Obiang Mbasogo.

The Cape Town court ordered the seizures to compensate local businessman Daniel Janse van Rensburg for about $2.2-million he claimed against the vice-president for unlawful arrest and torture.

He said he was unlawfully detained in Equatorial Guinea for about 500 days after a business deal went wrong.

Days after the court order, on 9 February, Potgieter and Huxham were arrested in the capital, Malabo, where they were working for the Dutch company SBM Offshore. They are both "highly experienced and professional engineers", their families said.

They were arrested on "trumped-up allegations of drug-related charges. They were wrongfully convicted and sentenced to 12 years of imprisonment,...