A large team of Chinese health workers arrived in Liberia to boost the Ebola fight as a US-based doctor infected in Sierra Leone was described as being "extremely ill".

The 160-strong Chinese deployment to the west African country worst hit by the virus came as the world's most powerful economies vowed to "extinguish" the epidemic which has claimed more than 5,100 lives.

The Chinese doctors, epidemiologists and nurses will staff a $41 million (33 million euro) Ebola treatment unit which will be built and be up and running in 10 days, ambassador Zhang Yue said in a statement on Sunday.

The health workers have had previous experience in tackling the SARS (Severe Acute Respiratory Syndrome) in Asia, Zhang said, adding that its total aid to Liberia would be $46 million.

At least 2,812 people have so far died of Ebola in Liberia.

So far Beijing has promised Ebola-hit countries the equivalent of $122 million to help fight the epidemic.

Since the beginning of the year, China has given west African countries a total of 234 million yuan ($38.2 million) in emergency assistance, including disease prevention and control materials, grain and cash, according to the Chinese foreign ministry.

China is Africa's largest trading partner, and its diplomatic footprint across the continent has expanded hugely in recent years as it seeks resources to power its economy.

Still it is a long way behind the European Union, whose leaders have boosted their Ebola aid to one billion euros ($1.26 billion).

- 'Hour by hour situation' -

Meanwhile a doctor said to be "extremely ill" after being infected with Ebola in Sierra Leone was being treated in the United States.

Martin Salia, a US resident who was infected with the deadly haemorrhagic fever while treating patients in his home country, was flown to Nebraska for treatment.

"This is an hour-by-hour situation," said Phil Smith, medical director of the biocontainment unit at the Nebraska hospital, one of a handful of medical facilities in the United States specially designated to treat Ebola patients.

"He is extremely ill," Smith said. "We will do everything humanly possible to help him fight this disease."

World leaders meeting at the G20 summit in the Australian city of Brisbane said they were prepared "to do what is necessary to ensure the international effort can extinguish the outbreak".

The Ebola outbreak which began earlier this year has been centred around Guinea, Liberia and Sierra Leone.

- Charity single -

In London, musicians including boy band One Direction and Led Zeppelin's Robert Plant recorded a new "Band Aid" single to help raise funds combat the virus.

Other performers ranging from U2 frontman Bono, Coldplay's Chris Martin and Sinead O'Connor recorded late into the night for a 30th anniversary version of the charity single "Do They Know It's Christmas?"

"It's not just about what's happening in west Africa, it could happen here tomorrow," said rocker-turned-activist Bob Geldof, one of the forces behind the original Band Aid.

Set to be officially released Monday, the single will be the fourth incarnation of the song, which became one of the biggest-selling singles ever after its release in 1984 to raise funds for Ethiopian famine relief.

In Brisbane, G20 members welcomed an International Monetary Fund initiative to release $300 million to combat Ebola and promised to share best practices on protecting health workers on the front line.

The G20 pledge came as Togo, whose president is coordinating the west African fight, warned that the world "cannot relax efforts" despite some encouraging signals.

There is no known cure for Ebola, one of the deadliest known pathogens, but trials for several possible treatments were announced this week in west Africa and Canada. The disease spreads through contact with bodily fluids.

The World Health Organization said Friday that 5,177 people are known to have died of Ebola across eight countries, out of a total 14,413 cases of infection, since December 2013.

UN chief Ban Ki-moon urged "G20 countries to step up," warning that Ebola's disruptive effect on farming could potentially spark a food crisis for a million people.

"Transmission continues to outpace the response from the international community," Ban told reporters.

burs-ach/txw