An Ebola epidemic in a conflict-riven region of Democratic Republic of Congo is out of control and could become as serious as the outbreak that devastated three countries in west Africa between 2013 and 2016, experts and aid chiefs have warned.

New cases over the past month have increased at the fastest rate since the outbreak began last year, as aid agencies struggle to enact a public health response in areas that have suffered decades of neglect and conflict, with incredibly fragile health systems and regular outbreaks of deadly violence involving armed groups.

“I’m very concerned – as concerned as one can be,” said Jeremy Farrar, the head of the Wellcome Trust, who called for a ceasefire to allow health teams to reach the sick and protect others in the community.

“Whether it gets to the absolute scale of west Africa or not, none of us know, but this is massive in comparison with any other outbreak in the history of Ebola and it is still expanding. It’s remarkable it hasn’t spread more geographically but the numbers are frightening and the fact that they are going up is terrifying.”

A six- to nine-month ceasefire, brokered by the UN, the Red Cross or similar bodies, is vital to stopping the spread, he said. “There was violence in west Africa, in Freetown and Monrovia, but this is on a different scale and it is coming from multiple sources.”

More than 1,600 people have been infected with the Ebola virus in the North Kivu region of DRC and more than 1,000 have died so far – the great majority women and children. At least 10 months since the outbreak began, the numbers are rising steadily and the fatality rate is higher than in previous outbreaks, at about 67%.

Returning from a visit to his teams in the region, David Miliband, the head of the International Rescue Committee, called for a “reset” in the response. “The situation is far more dangerous than the statistic of 1,000 deaths, itself the second largest in history, suggests and the suspension of key services threatens to create a lethal inflection point in the trajectory of the disease,” he said. “The danger is that the number of cases spirals out of control, despite a proven vaccine and treatment.”

IRC teams, who have had three triage units in health centres burned down, have warned that the situation in North Kivu is increasingly volatile and is making progress against the disease impossible. Last week, fighters from the armed Mai-Mai rebel group attacked a treatment centre in Butembo, one of the towns at the centre of the crisis. This week, two patients were killed during an assault on a treatment centre in Katwa, the second such incident in the town this month.

Facebook Twitter Pinterest Health workers lift a coffin carrying Kahumbu Ngalyakuthi, who was infected after sharing a hospital room with a patient with Ebola in North Kivu. Photograph: Hugh Kinsella Cunningham/EPA

The WHO director general, Dr Tedros Adhanom Ghebreyesus, has also voiced profound disquiet. In March, Dr Tedros said the Ebola outbreak was contracting and would be over in six months. After a visit at the end of April with the regional director for Africa, Dr Matshidiso Moeti, he said he was deeply worried about the situation. “Cases are increasing because of violent acts that set us back each time,” he said.

The pair went to Butembo, where a WHO epidemiologist, Dr Richard Mouzoko, was killed by armed men while he and colleagues were working on the Ebola response.

“We are entering a phase where we will need major shifts in the response,” said Dr Tedros. “WHO and partners cannot tackle these challenges without the international community stepping in to fill the sizeable funding gap.” Only half of the currently requested funds have been received, which could lead to WHO and partners rolling back some activities when they are most needed.

Those on the frontline in North Kivu fear no end is in sight. Whitney Elmer, a country director for Mercy Corps, one of the humanitarian NGOs working on preventing the spread, said there had been “a drastic change in the security situation”, which was causing a big rise in the number of cases.

Elmer said there had been about 400 cases over the past month – the highest figure for that time period since the outbreak began – and the number of new cases was increasing at a much higher rate than seen previously.

“We are very concerned,” she said, adding that there was real potential for the outbreak to spread to neighbouring Rwanda or Uganda.

Frontline workers say there has not been enough community involvement and that bringing in armed police and especially cancelling elections in the region have provoked hostility and suspicion. “The overall strategy has been to go full force to do things as quickly as possible,” said Elmer. She added that it was vital that local people and organisations were included in decision-making.

Médecins Sans Frontières, whose volunteer doctors have been at the forefront of every Ebola outbreak, agreed that the failure to engage communities had been a disaster.

“We are very concerned and the signs around the outbreak response are not good right now,” said Kate White, one of its emergency managers.

New cases should be picked up by routine surveillance and testing the contacts of people who fall ill. “But what we see right now is that the majority of confirmed cases are coming through community deaths. It’s a very worrying sign,” she said. “It means communities are not aware or not active participants in the response. People die in their communities and they have the ability to transmit the virus to as many people as possible.”

She said agencies needed to have the local people actively working against Ebola. “Anything else is a band-aid solution.”

WHO recently announced an expansion of the vaccination guidelines and the introduction of a second vaccine to try to protect people. Experimental drugs have also been given to 700 people, although nobody yet knows how successful they have been. But unless it is possible to reach affected communities with vaccines and drugs, the new technologies are useless.

“The tragedy is that we have the technical means to stop Ebola, but until all parties halt attacks on the response, it will be very difficult to end this outbreak,” Dr Tedros tweeted on Friday.