GOMA, Democratic Republic of Congo (Reuters) - Three Congolese doctors have been arrested for allegedly planning an attack on a hospital that killed a senior World Health Organization (WHO) epidemiologist involved in the Ebola response, a prosecutor said on Wednesday.

Cameroonian doctor Richard Mouzoko was killed in an attack in April on a hospital in the city of Butembo, one of the epicenters of the year-long Ebola outbreak, which is the second deadliest in history.

Ebola treatment centers have repeatedly been attacked by armed militiamen and disgruntled locals, hampering efforts to contain the epidemic in Democratic Republic of Congo’s conflict-ravaged east.

Lieutenant Colonel Jean-Baptiste Kumbu, a senior military prosecutor, said militiamen involved in attacking treatment centers had, under interrogation, implicated four doctors in planning the raids, including against the Butembo hospital.

Kumbu said three had been arrested, while the fourth was at large. He provided no further details about when or where they were detained or what their motive might have been.

In a statement, the Butembo branch of Congo’s national doctor’s council said it was “indignant” over the arrests, which it said were crippling vital medical services in the area.

It said the doctors should be released on bail, and that medical personnel would launch a strike within 48 hours if they were not.

Despite the deployment of a highly effective vaccine, Ebola has continued to spread in eastern Congo, reaching the region’s largest city of Goma last month. The most recent outbreak has killed more than 1,800 people since last year, according to Congolese health authorities.

Some people believe that Ebola is a conspiracy cooked up by the government or foreign countries. The influx of donor money to fund the response has also fueled tensions between rival political leaders and economic operators, leading in some cases to violence.

Kumbu said a total of 54 people are currently under arrest in connection with attacks on Ebola treatment centers.