The Ebola outbreak in the Democratic Republic of Congo is now reported to be in two areas and could be stopped by September, but the country also needs help strengthening its broader health problems, the head of the World Health Organization said on Thursday.

The outbreak is recorded as the the second worst in history, and it is believed to have killed 587 people in a region that is known for violence and poverty. A quick international response has so far stopped the disease spreading into neighboring countries.

"We have averted a much larger outbreak," said WHO chief Tedros Ghebreyesus Adhanom, adding that the affected area was contained and shrinking. "Our target now is to finish it within the next six months."

The number of new cases is now 25 per week since January, which is half of what was recorded prior and the virus was now concentrated in two towns, Butembo and Katwa. However, attacks by armed groups and community distrust from outside help were slowing down the response and extended help. 

On Thursday, a group of young men attacked an Ebola center for the fifth time since last month, Congo's health ministry said, after medics tried to collect samples from the body of a man that died of the virus.

Police opened fire to alert the crowd in the Biena health zone, west of Butembo, but it killed one person and injuried another, the ministry said in a statement.

Last week the head of medical charity MSF, which had two facilities attacked, said the battle against Ebola was deemed difficult because the locals did not trust health workers and the response was militarized.

Tedros, who has just returned from the outbreak area, said local people were wondering why the world was so worried by Ebola while caring so little about other health problems like cholera and malaria.

"I'd actually like to call upon the international community to link the outbreak control now with developing the health system," he said. "That's a big challenge. Otherwise, we will appear as if we are preventing Ebola getting into other countries and we don't care about the demands of the community."

He said the WHO would not leave the Congo when the outbreak ended but would help the government to build stronger and more stable health services.

He called on international donors to fund the $148 million plan to fight Ebola from spreading in the next six months, a tiny amount to spend compared to the potential cost. The worst outbreak, which killed 11,300 people in West Africa in 2013-2016, cost around $53 billion, according to a study.