A patient in Sweden who was admitted to hospital with a suspected case of Ebola, was found not to be suffering from the highly infectious and potentially fatal disease, healthcare officials have said.

"The young man... who had symptoms... is not suffering from Ebola. That is what the result of tests shows," the health authorities in Uppsala, about 70 kilometres (45 miles) north of Stockholm, said in a statement on Friday.

The regional authority said the man's condition had improved over the course of the day and that while tests had also ruled out diseases such as Marburg and dengue fever, further examinations were needed to determine the nature of the illness.

Patients at the emergency ward in Enkoping had also been kept isolated pending the test results, as were the man's relatives, but all were now free to go home, it said.

"The patient came in this morning. He was throwing up blood and had bloody stools," which can be a symptom of Ebola, Mikael Kohler, a medical director for Uppsala Region, told AFP earlier on Friday.

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The young man, whose identity has not been released, lives in Sweden and had returned from a trip to Burundi three weeks ago but was not known to have visited any Ebola-contaminated area, Kohler said.

The symptoms first appeared on Friday morning.

An Ebola outbreak in the Democratic Republic of Congo has killed 356 of the 585 people known to have been infected over the past six months.

The epidemic in a volatile part of Congo is the second worst ever, according to the World Health Organization (WHO).

The largest outbreak was one in 2013-2016 in West Africa, where more than 28,000 cases were confirmed.