A South African doctor who dedicated himself to saving the lives of black children from cancer throughout the apartheid era has been refused bail by a court in Abu Dhabi, where years ago he was accused and convicted without his knowledge of killing a young leukaemia patient.

Cyril Karabus pioneered treatment for cancer and blood disorders at the Red Cross hospital in Cape Town, where he worked for 35 years, and trained numerous doctors at Cape Town University, some of whom work at the Great Ormond Street and Whittington hospitals in London.

Now 77, he has been returned to the jail in Abu Dhabi where he has been confined for the last two months. "He is an old, frail and very sickly man," said his lawyer, Michael Bagraim. "He has no travel documents or any means of escaping or jumping bail. There doesn't seem to be any heart in what is taking place.

"My reports from people who were in the court were that the man appears to be broken. He was hunched. He was shackled. He is almost 78 and he has a pacemaker and a stent because of problems with his heart. He appears to have his spirit broken as well. Yet the man has not done anything wrong."

The first Karabus knew of the 10-year-old criminal conviction against him was after he was arrested at Dubai airport on 18 August as he changed flights on his way home from his son's wedding in Canada. He had no knowledge of a complaint about his treatment, 12 years ago, of a three-year-old child while he was working as a locum at the Sheikh Khalifa Medical Centre in Abu Dhabi. He had reached retirement age in South Africa but loved his work and could not, in any case, afford to get by on a state pension.

His daughter Sarah, a paediatrician in Cape Town, who was travelling with him, said: "We have all been completely traumatised by it. We are a big family. We were together for the first time in years at my brother's wedding. We came from a joyous occasion and then this happened. The family is depressed and angry."

They had all been given 24-hour visas to go to a hotel because they had a 10-hour stopover in Dubai. When they returned to board the plane, she and her husband and two children went through the passport check before her parents, so she did not see what happened next.

"My mother said they were standing at passport control when a man in a suit came up to him and said: 'Come with me, I'm police.' My father asked his name. He said: 'I don't have to tell you, I'm police.' My mother was given five minutes with him. She was told she couldn't stay in the country."

The family said they all believed it must have been a mistake, or at least that he would be allowed home while he challenged the conviction. However, Karabus has been in jail ever since, even though his lawyers had the original conviction overturned on the basis that he had not been told of the complaint, and therefore had not had a chance to defend himself.

He faces new charges of manslaughter and was refused bail at the fourth hearing in the case, at which authorities were given more time to find the files, which have all gone missing.

"They can't even find the files to make the allegations," Bagraim said. "They can't find the family of the deceased girl. They have nothing.

"He is probably one of the leading experts in paediatric oncology. He is telling the court, 'I have done nothing wrong and if I had to do it again, I would do the same thing'. This was acute leukaemia. The kid was going to die anyway. There was nothing he could do but make her comfortable."

The World Medical Association, an international organisation representing doctors, has written to the United Arab Emirates justice minister to express its "deep concern about Professor Karabus and the state of his health", and its surprise that he has not been granted bail. It said it would follow any trial closely.

Many other doctors have expressed support, and Sarah Karabus said she was answering 80 to 100 emails a day from wellwishers. Her father has been moved to the medical wing of the prison where he is being held, and has been allowed a chess set and some books.

Bagraim said the South African government did not want to interfere in another country's justice system, but he felt it could do more. "He [Karabus] has done the country proud. He saved the lives of the poorest of the poor. During the apartheid system, he concentrated on helping children of colour, so much so that he is an impoverished man himself today." The next hearing is set for 11 October.