Angry residents of a town at the epicenter of the Ebola outbreak in eastern Congo attacked and burned a tent that was part of a health center where people are being treated for the virus, the staff there said Saturday. It was the second such attack in the region in a week.

No one was hurt in the attack, according to initial reports but as patients ran out to escape the fire, 18 people with suspected Ebola infections left the facility and are now unaccounted for, a local hospital director said.

The angry residents had arrived at the clinic in the town of Mongbwalu on Friday night and set fire to a tent set up for suspected and confirmed Ebola cases by the Doctors Without Borders humanitarian group, Dr. Richard Lokudi, director of the Mongbwalu hospital, told The Associated Press.

"We strongly condemn this act, as it caused panic among the staff and also resulted in the escape of 18 suspected cases into the community," he said.

On Thursday, another treatment center, in the town of Rwampara, was burned down after family members were banned from retrieving the body of a local man suspected to have died of Ebola.

Burials of Ebola-victims stir anger, frustration

The bodies of those who died of Ebola can be highly contagious and lead to further spread when people prepare them for burial and gather for funerals. The dangerous work of burying suspected victims is being managed wherever possible by authorities, which can be met by protests from families and friends.

A communal burial for Ebola patients in Rwampara took place on Saturday under tight security as tensions between health workers and the local community ran high, said David Basima, a team leader with the Red Cross overseeing burials.

Armed soldiers and police monitored the burials as Red Cross workers clad in white protective suits lowered sealed coffins into the ground. Crying family members stood at a distance.

Basima said his team, after arriving at the scene, "experienced a lot of difficulties, including resistance from young people and the community."

"We were forced to alert the authorities so that they could come to our aid, just for safety," said Basima.

Authorities in northeastern Congo on Friday banned funeral wakes and gatherings of more than 50 people in an effort to curb the spread of the virus.

The outbreak is a high risk to Congo, WHO says

The World Health Organization has said that the outbreak now poses a "very high" risk for Congo — up from a previous categorization of "high" — but that the risk of the disease spreading globally remains low.

WHO Director-General Tedros Adhanom Ghebreyesus said Sunday that 101 cases have been confirmed in Congo.

There is no available vaccine for the Bundibugyo virus, a rare type of Ebola, which spread undetected for weeks in Congo's Ituri province following the first known death, while authorities tested for another, more common, Ebola virus and came up negative. There are now more than 900 suspected cases and 204 suspected deaths, though more are expected as surveillance expands, Ghebreyesus said.

One American doctor working with a missionary group in Congo has tested positive, and several others are believed to have been exposed.

Dr. Jean Kaseya, director-general of the Africa Centers for Disease Control and Prevention, said a response to the outbreak must include building trust with communities.

The International Federation of Red Cross and Red Crescent Societies said Saturday that three of its volunteers had died from the outbreak in Mongbwalu. The agency said it believed the three healthcare workers contracted the virus on March 27 while handling dead bodies as part of a humanitarian mission unrelated to Ebola.

If confirmed, this would significantly push back the timeline of the outbreak from the previous first confirmed death in late April in the town of Bunia, the capital of Ituri.

The US bars green-card holders from Ebola-stricken countries

U.S. federal health officials said on Friday night that they are banning green card holders who have been in Ebola-affected countries from returning to the U.S.

Green card holders are people who are not U.S. citizens but have been granted authorization to live and work permanently in the United States.

According to a Federal Register notice on Friday, the U.S. government is enacting a rule that restricts green card holders who have recently been in Congo, Uganda or South Sudan from reentering the United States.

It's unclear why South Sudan was on the list as the country has not confirmed any Ebola cases so far in this outbreak.

Such a ban will help ensure that Ebola screening, contact tracing, quarantine monitoring, and medical monitoring will be available to U.S. citizens, according to the notice.

Federal law provides for a period before such decisions become final but the U.S. Department of Health and Human Services can argue that the order can take effect immediately in certain circumstances.

The department did not immediately respond to a request for comment.