The NGO Médecins Sans Frontières has expressed concern over the rising number of Ebola cases in the Democratic Republic of Congo.

The aid agency says it is particularly concerned that the outbreak has now reached the city of Butembo, home to one million people.

In response, MSF has increased the capacity of its Ebola treatment centre (ETC) in Butembo to 64 beds.

So far, 440 people in DRC have been infected with the virus, leading to the deaths of 255 people.

There have also been newly found cases in Kalenguta, 25km to the north of Butembo, and Katwa, 30km to its east.

The Ebola outbreak in eastern Congo is now the worst in the country's history and the second biggest recorded outbreak in Africa, according the the country's health ministry.

The epidemic in a volatile part of Democratic Republic of Congo is now only surpassed by the 2013-2016 outbreak in West Africa, where more than 28,000 cases where confirmed, and is bigger than an outbreak in 2000 in Uganda involving 425 cases.

MSF has said that this outbreak will continue and that efforts must be increased to bring it under control by reaching isolated communities to administer treatment, decontamination of health centres and vaccination health workers.