The World Health Organization said Tuesday that fighters in conflict-ravaged Sudan had occupied the national public laboratory holding samples of diseases including polio and measles, creating an "extremely, extremely dangerous" situation.

Fighters "kicked out all the technicians from the lab... which is completely under the control of one of the fighting parties as a military base," said Nima Saeed Abid, the WHO's representative in Sudan.

He did not say which of the fighting parties had taken over the laboratory.

Abid said he had received a call from the head of the national laboratory in Khartoum Monday, a day before a US-brokered 72-hour ceasefire between Sudan's warring generals officially came into effect after 10 days of urban combat.

"There is a huge biological risk associated with the occupation of the central public health lab," said Abid.

He pointed out that the lab held so-called isolates, or samples, of a range of deadly diseases, including measles, polio and cholera.

The director of the lab had also warned of the danger that "depleting stocks of blood bags risk spoiling due to lack of power," Abid said.

"In addition to chemical hazards, bio-risk hazards are also very high due to lack of functioning generators," he said.

The UN health agency also said that it had confirmed 14 attacks on healthcare during the fighting, killing eight and injuring two.

The fighting in Sudan has pitted forces loyal to army chief Abdel Fattah al-Burhan against those of his former deputy Mohamed Hamdan Daglo, who commands the Rapid Support Forces (RSF).

The Sudanese health ministry has put the number of deaths so far at 459, with a further 4,072 wounded, the WHO said Tuesday, adding that it had not be able to verify that number.