BENI, Congo (AP) — Rebels again attacked a city at the center of the Ebola outbreak in eastern Congo, killing at least six people including a pregnant woman, witnesses and officials said Saturday.

Meanwhile, Congolese health authorities said a spate of recent violence in the area has allowed the Ebola virus to spread further, a new setback in the 16-month outbreak.

The new attack in Beni on Friday night came as Congo's military steps up its fight against armed groups including the Allied Democratic Forces rebels. They were blamed for the assault.

Omar Kavota, president of a local human rights group known as CEPADHO, said the attack began around 8:30 p.m.

A recent surge in such assaults has led some Beni residents to protest violently over the lack of protection for civilians. Last month residents burned the town hall and stormed the United Nations peacekeeping mission.

Repeated attacks by ADF rebels and other armed groups also have disrupted health workers' efforts to contain Ebola, which has killed more than 2,200 people in this outbreak. Vaccination teams at times have been unable to reach those most at risk because of the threat of violence.

On Saturday, Dr. Jean-Jacques Muyembe, who leads Congo's Ebola response, told reporters a new spike in cases has been observed following recent attacks in the region. One attack last month killed four Ebola responders including a member of a vaccination team.

Thirty-four new cases were recorded between Nov. 29 and Dec. 11, according to Muyembe.

Congolese President Felix Tshisekedi on Friday promised to do everything possible to stop the ADF and other armed groups who have operated in the region for years.

"Our determination is total and unwavering to eradicate them," he said in his state of the nation address. He took office in January.