The World Health Organisation has issued an unusual statement raising questions about whether Tanzania is covering up possible cases of the deadly Ebola virus.

The disease is a significant cause for concern during a regional outbreak that has been declared a rare global health emergency.

The statement says Tanzania’s government “despite several requests” has not shared its clinical data, the results of its investigations or the possible contacts of a number of patients with Ebola-like symptoms.

Tanzania’s government, which has said it has no Ebola cases, could not immediately be reached for comment. The cases would be the first ever Ebola infections confirmed in the East African country.

The United Nations health agency says it was made aware on September 10 of the death in Tanzania’s commercial capital, Dar es Salaam, of a patient suspected to have Ebola.

A day later, it received unofficial reports that an Ebola test had come back positive.

On Thursday, it received unofficial reports that a contact of the patient, who had travelled widely in the country, was sick and in hospital.

A rapid response is crucial in containing Ebola, which can be fatal in up to 90% of cases and is most often spread by close contact with bodily fluids of people exhibiting symptoms or with contaminated objects.

The WHO statement said the lack of information from Tanzania made it difficult to assess potential risks.

The Ebola outbreak based in neighbouring Democratic Republic of Congo has infected over 3,000 people and killed nearly 2,000 of them.

A few cases have been confirmed in neighbouring Uganda as well, and other neighbouring countries have been preparing for the outbreak’s possible spread.

This is not the first time health officials have raised serious questions about the suspected Tanzania cases.

On Monday, the US health and human services secretary, Alex Azar, told reporters in Uganda that he and others were “very concerned about the lack of transparency” in Tanzania.

Critics have shown increasing alarm as Tanzanian President John Magufuli’s government has restricted access to key information and cracked down on perceived dissent.

Politicians recently approved an amendment to a statistics law to make it a crime to distribute information not sanctioned by the government or which contradicts the government.

The World Bank was among those expressing concern at that amendment.