DAKAR, Senegal -- Two infected patients who fled from an Ebola treatment center in a Congo city of 1.2 million people later died, an aid group said Wednesday while asserting that "forced hospitalization is not the solution to this epidemic." As the number of suspected Ebola cases continued to rise, experts emphasized that more community engagement is needed to prevent the spread of the deadly virus.

Three patients left of their own accord from the isolation zone of the Wangata hospital in Mbandaka city between Sunday and Tuesday, said Henry Gray, emergency coordinator for Medecins Sans Frontieres, or Doctors Without Borders.

One patient had been about to be discharged, he said. "The two others were helped to leave the hospital by their families in the middle of the night on Monday. One of the men died at home and his body was brought back to the hospital for safe burial with the help of the MSF teams; the other was brought back to the hospital yesterday morning and he died during the night," Gray said in a statement.

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Hospital staff made every effort to convince the patients and their families not to leave and to continue treatment, Gray said.

Health ministry sources told the Reuters news agency that two police officers were assigned to help track the two patients down.

Three Ebola deaths have been confirmed since Congo's health ministry announced the current outbreak of the often lethal hemorrhagic fever on May 8. It was not immediately clear if the two deaths reported by MSF were confirmed Ebola ones.

Congo's health ministry on Wednesday announced six new suspected cases in the rural Iboko health zone in the country's northwest and two in Wangata. There are now 28 confirmed Ebola cases, 21 probable ones and nine suspected. Overall the death toll stands at 27.

"We're on the epidemiological knife's edge of this response. The next few weeks will really tell if this outbreak is going to expand to urban areas or if we're going to be able to keep it under control," Dr. Peter Salama, the World Health Organization emergencies chief, told a World Health Assembly session Wednesday.

Residents arrive at the Wangata Reference Hospital in Mbandaka, Democratic Republic of Congo, May 20, 2018. Reuters/Kenny Katombe

Worrying factors include the spread of confirmed cases to Mbandaka city and the fact that five health workers have been infected, signaling "a potential for further amplification," he said. Front-line workers are especially at risk of contracting the virus, which spreads in contact with the bodily fluids of infected people, including the dead.

Finally, Salama said, the outbreak has "three or four separate epicenters," making it more challenging to contain. "It's really the detective work of epidemiology that will make or break the response to this outbreak. It's documenting how people are getting infected and therefore managing to control the transmission," he said.

"We are following three separate chains of transmission," he said. "One associated with a funeral that took place in a neighboring town of Bikoro; one associated with a visit to a health care facility more than 80 kilometers (50 miles) away in the small village of Iboko and one where we're still gathering data on that's related to a church ceremony."

WHO is accelerating efforts with nine countries neighboring Congo to try to prevent the Ebola outbreak from spreading beyond the border.

The top two priorities are Central African Republic and the Republic of Congo near the epicenter of the outbreak, Matshidiso Moeti, WHO's director for Africa, told the WHA session. The other countries are Angola, Burundi, Rwanda, South Sudan, Tanzania, Zambia and, to a lesser extent, Uganda.

WHO began vaccinations this week and is using a "ring vaccination" approach, targeting the contacts of people infected or suspected of infection and then the contacts of those people. More than 600 contacts have been identified, WHO said.

There is no specific treatment for Ebola. Symptoms include fever, vomiting, diarrhea, muscle pain and at times internal and external bleeding. The virus can be fatal in up to 90 percent of cases, depending on the strain.

The U.K. on Wednesday pledged another 5 million pounds ($6.6 million) to help combat the outbreak.

WHO Director-General Tedros Adhanom Ghebreyesus said simply: "We are watching it around the clock, 24-7."