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A “high risk of biological hazard” threatens Khartoum after one of Sudan's warring parties seized a laboratory holding measles and cholera pathogens and other hazardous materials, the World Health Organisation said on Tuesday.
Technicians were unable to access the National Public Health Laboratory to secure the materials, the WHO's Nima Saeed Abid said from Geneva.
“This is the main concern — no accessibility to the lab technicians to go to the lab and safely contain the biological material and substances available,” he said.
The WHO did not say which side had seized the laboratory.
Fighting between the army and the paramilitary Rapid Support Forces broke out on April 15, turning residential areas into war zones.
At least 459 people have been killed and more than 4,000 wounded.
More gunfire, explosions and warplanes flying overhead were reported on Tuesday after the start of a US and Saudi-brokered 72-hour ceasefire.
Access to water, power and food has been cut in a nation already reliant on aid.
Sudan violence 'risks catastrophic conflagration', warns UN chief
The UN's humanitarian office, OCHA, has been forced to cut back on some of its activities in parts of Sudan due to intense fighting.
At least five aid workers have been killed since fighting broke out and the two UN agencies who lost staff, the International Organisation for Migration and the World Food Programme, have suspended their activities.
“In areas where intense fighting has hampered our humanitarian operations, we have been forced to reduce our footprint,” said Jens Laerke, spokesman for OCHA. “But we are committed to continue to deliver for the people of Sudan.”
He said an OCHA team would be leading humanitarian operations out of Port Sudan after transferring from Khartoum.
Patrick Youssef, regional director of the International Committee of the Red Cross, urged other countries to keep up pressure on Sudan to find a “long-lasting solution”, even after foreigners had been evacuated.