At least two Ebola health workers in eastern Congo have been reportedly killed by unidentified men.

The killing over the weekend is said to be the latest in a string of assaults that have hobbled efforts to contain the second largest ever epidemic of the deadly virus, the health ministry said.

According to Reuters, the two people, who were community workers near Mukulia in North Kivu province, had been receiving threats since last December and one had previously been attacked, the ministry added.

Attacks on treatment centers by armed groups and mistrust among residents who view the disease as a conspiracy have become major impediments to containing Democratic Republic of Congo’s worst-ever Ebola outbreak.