At least 131 deaths have been reported in an Ebola outbreak in the Democratic Republic of Congo, with more than 513 cases suspected, local officials have said.

A spokesman for the DR Congo government said cases were now being reported over a wider area.

There are also two confirmed cases and one death in Uganda, says the US Centers for Disease Control and Prevention (CDC).

The World Health Organization (WHO) has declared the outbreak of the current strain of Ebola, which is caused by the Bundibugyo virus, an international emergency.

As this deadly Ebola outbreak continues to spread, the Congolese government has sought to reassure people that its response teams are working hard to trace and investigate suspected infections - and that there is no need for panic.

However, with cases now identified in new areas including Nyakunde in Ituri Province, Butembo in North Kivu, and the city of Goma, concern is inevitably growing.

An American doctor in the DR Congo is among those with a confirmed case, the medical missionary group they were working with and the CDC has said.

The individual will now be taken to Germany for treatment, they told CBS News, the BBC's US partner.

While the CDC did not name the American working in the country, medical missionary group Serge said one of its US doctors, Peter Stafford, had tested positive for Ebola.

Two others doctors from the group who were exposed while treating patients, including Stafford's wife, Dr Rebekah Stafford, did not have symptoms and were following quarantine protocols, the group said in a statement.

CBS News also quoted sources as saying that at least six Americans have been exposed to the Ebola virus during the outbreak in the DR Congo.

The CDC said it was supporting the "safe withdrawal of a small number of Americans who are directly affected", but did not confirm how many.

The US government is reportedly looking to arrange transport for the small group of Americans in DR Congo to a safe quarantine location, a source told health news site STAT.

Quoting a source, the site adds that the group could be taken to a US military base in Germany, though this has not been confirmed.

The CDC declined to answer direct questions about the US citizens reportedly affected during a press conference on Sunday.

In an update on Monday, the public health agency said the risk to the US was relatively low, but said it would introduce a range of measures to prevent the disease from entering the country.

This includes monitoring travellers arriving from affected areas and placing entry restrictions on non-US passport holders if they have been in Uganda, DR Congo or South Sudan in the last 21 days.

The CDC said it would work with airlines and other partners to carry out contact tracing of passengers, increase testing capacity and hospital readiness to respond to the outbreak.

The US has also issued a Level Four travel advisory - its most severe level - warning against travel to the DR Congo.

The WHO has said the outbreak in DR Congo's eastern Ituri province is a public health emergency of international concern, but did not meet the criteria of a pandemic.

The agency has also warned it could potentially be "a much larger outbreak" than what is currently being detected and reported, with significant risk of local and regional spread.

More than 28,600 people were infected by Ebola during the 2014-2016 outbreak in West Africa, the largest outbreak of the virus since its discovery in 1976.

The disease spread to a number of countries within and outside of West Africa, including Guinea, Sierra Leone, the United States, the United Kingdom and Italy, killing 11,325 people.

Jean Kaseya, the head of the Africa Centres for Disease Control and Prevention, told the BBC earlier that the number of suspected cases had reached almost 400.

He said that in the absence of vaccines and effective medicines people should follow public health measures, including the guidance about handling the funerals of those who have died from the disease.

"We don't want people infected because of funerals," he told the BBC World Service's Newsday programme.

Community funerals, where people helped wash the bodies of their loved ones, contributed to many people becoming infected in the earlier stages of the big outbreak more than a decade ago.

The WHO has advised DR Congo and Uganda, two countries with confirmed cases, to undertake cross-border screenings to avoid the virus spreading.

It has also urged nearby countries to "enhance their preparedness and readiness", including surveillance at health facilities and communities.

Neighbouring Rwanda said it would be tightening screening along its border with DR Congo as a "precautionary measure", while Nigeria said it was "closely monitoring the situation".