Petr Jašek, the Czech Christian freed from prison in Sudan, has spoken of the beatings and humiliation inflicted on him there.

Jašek spent 14 months in jail under Sudan's oppressive Islamist regime accused of inciting hatred and spying. He had been in the country investigating reports of the persecution of Christians and was originally sentenced to 24 years in prison.

Two Sudanese believers, Rev Hassan Abdelrahim and Abdelmonem Abdumawla, were also sentenced to long jail terms and are still imprisoned.

Jašek was moved from prison to prison – five in total – with 'each getting worse and worse', he told Czech reporters on Sunday.

He said: 'The first two months were probably the most severe for me because I was placed in a cell together with members of the Islamic State, who humiliated me as a Christian. It then escalated into humiliation and physical beatings, and psychological torture and humiliation.'

One prison was known as 'the refrigerator' because prisoners were subjected to constant blasts of cold air; he said it was 'terrible'.

He said one of the hardest blows for him during the imprisonment was finding his father had died a month after it had happened.

He had been nicknamed 'Karl Marx' by other prisoners due to the bushy beard he grew, but that was shaved off just before his release. Friends said he looked well, though he has lost 25kg in weight.

Czech foreign minister Lubomir Zaoralek praised his courage, saying: 'The conditions were very heavy. I am convinced that he is really an extraordinarily brave guy. Most people could not stand it.'

Jašek had an emotional reunion with his wife Wanda, who was sitting on a crowded train when she got the news of his release. A close friend described how tears were streaming down her face, to first the surprise, then delight of other passengers.

Jašek urged supporters not to forget the two men still in Sudan's Kober prison, sentenced to 12 years each for aiding him.

Christian Solidarity Worldwide's CEO Mervyn Thomas said: 'It is deeply regrettable that the amnesty granted to Mr Jašek was not extended to his co-defendants, particularly in view of the fact that the case against them was predicated on his alleged actions and conviction. These men remain in a maximum security prison despite the evidence against them being so weak that the case should not have proceeded to trial, let alone resulted in such lengthy convictions.

'CSW calls on the Sudanese Government to review and overturn the verdict and sentences given to Revd Abduraheem and Mr Abdumawla. We also call on the EU to urge Sudan to expedite the release of the men so that they too can return to their families.'