Democratic Republic of Congo's fast-spreading Ebola outbreak is now the world's second-largest on record, government data showed on Friday, as transmission continues to outpace efforts to contain the epidemic.

The number of cases reported across Congo has risen to 3 532, the Communications Ministry said in a statement, with 1 556 deaths recorded.

"It's the fastest-spreading Ebola epidemic that we have ever seen," Carl Skau, acting head of the UN World Food Programme, told Reuters this week. "The world needs to pay much more attention."

Less than three months since the outbreak began, the disease has killed five times as many people as previous outbreaks had by the same stage, according to Africa's top public health agency, the Africa Centres for Disease Control and Prevention.

The outbreak is caused by the rare Bundibugyo strain of the Ebola virus, which has no approved vaccine or treatment.

Health responders are also battling insecurity and attacks on health facilities across eastern Congo, where dozens of armed groups operate, while deep foreign aid cuts have stretched resources.

The latest figures about the outbreak indicate that only West Africa's 2014 to 2016 outbreak was bigger, with 28 616 cases and 11 310 deaths recorded across Guinea, Liberia and Sierra Leone, according to the World Health Organization. 

WHO SAYS OUTBREAK MAY BE BIGGER THAN REPORTED

Angele Gapio, head of emergencies for the Caritas charity in the northeastern city of Bunia, said awareness campaigns were failing and frontline responders were exhausted and traumatised.

"The disease has now settled in the community," she told Reuters. "People continue to seek treatment from traditional healers, and the chain of transmission continues."

The WHO said earlier this month the true scale of the outbreak could be up to four times higher than official figures suggest.

Reuters reported this week that surveillance efforts are stretched due to shortages of vehicles, understaffing and community mistrust. 

MORE FUNDS NEEDED TO CONTAIN EPIDEMIC

Africa CDC said in June it would require $1.4-billion to contain the Ebola outbreak, three times its earlier estimate. 

Figures presented this week by Africa CDC and the WHO showed Congo's May-August response plan had secured $213.9-million in declared funding, short of planned spending of $242.4-million.

A US travel ban is also restricting the supply of aid workers. The Trump administration said earlier this month it was blocking American citizens in Congo from travelling to the US on commercial flights.

Samaritan's Purse, which operates treatment centres and relies on US responders for its mission in Congo, said it will have to scale back because of the quarantine order.