A man from Birmingham said he was devastated to learn his nephew had died as he struggled to get treatment for his diabetes in Sudan.
Hundreds of people have been killed in the conflict which began on 15 April.
Dr Fathi Jamil said his relative in Khartoum needed regular dialysis but the fighting had disrupted the 33-year-old’s vital treatment.
“One of his cousins was with him, he said he could not breathe and a few moments later he died,” he said.
“That for me is very difficult. I am devastated. I can’t even send them money to help.”
Dr Jamil, who manages two charities in Birmingham, said his five brothers and sisters were still in the country’s capital with their families.
The fighting has left many people who previously moved away from Sudan feeling helpless about the current situation, he added.
“I think many of us Sudanese in other countries feel bad because we are unable to do anything to help our people,” he said.
Meanwhile, a doctor from Birmingham who was stranded in Sudan with her three children was thought to have escaped the country, her employers said.
Her colleagues at City Hospital were urging the government to help senior registrar Dr Lina Badr and her family get home from Khartoum, in a petition on the Change.org website.
She was “a friend to many of us”, they wrote on the website and added they felt “fearful of the danger” she was in.
A spokesperson with Sandwell and West Birmingham Hospitals NHS Trust said they were told she had made it to Egypt with her children.
Contact with loved ones in Sudan has been sporadic since the fighting began, relatives have told the BBC.
Gamar Abdulrahim, an interpreter from Birmingham, said he had spoken to his uncle in Khartoum on Tuesday but feared it might be their last phone call.
“I still hear the gunshots in the background. He said that could be the last call to him. I told him not to lose hope,” he said.
“It has been nine nail-biting days, you cannot sleep well. You can do nothing.”
Mohammed Sameer, from Warwickshire, moved to the UK 10 years ago and said he was struggling to stay in contact with his family in Khartoum.
“It’s very spotty, the communication, so some days we are able to get in touch with our families back home, some days it is difficult,” he said.
“We have profound concern, anxiety and worry about the situation, our loved ones, families and the country as a whole.”
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