A triptych by Francis Bacon fetched $84.6 million on Monday at a Sotheby's auction held without an audience and live-streamed to bidders worldwide in a first for the company forced to adapt its big events during the coronavirus pandemic.

The British artist's work, inspired by Greek playwright Aeschylus's "Oresteia", is one of 28 large-scale triptychs - a painting in three parts - created by Bacon between 1962 and 1991.

It previously belonged to a Norwegian art collector and had an estimated value of $60-$80 million.

Sotheby's spring auctions usually generate billions of dollars, but with New York City hard-hit by COVID-19, the auction house announced last month it would stream a series of modern and contemporary art sales from London instead.

Describing the event as "an historic evening", Chairman for Sotheby's Europe Oliver Barker introduced the auction, the first of its magnitude to be held without an audience.

A bidding war raged for around 10 minutes between one potential buyer placing bids online from China, and another - who was victorious, but chose to remain anonymous - making counter-offers on the phone to a Sotheby's specialist in New York.

Another Bacon triptych, "Three Studies of Lucian Freud," sold in 2013 for $142.4 million at Christie's in New York, making it one of the 10 most expensive paintings ever sold at auction.

Sotheby's and Christie's 20th Century spring auctions sales usually occur at the same time, but Christie's announced earlier this month that it would hold its sale on July 10 this year.

While online bids have until now rarely exceeded $5 million, Jean-Michel Basquiat's drawing of a head, "Untitled (Head)" sold for $15.2 million on Monday - a new Sotheby's record for an online purchase - and a painting by Joan Mitchell, "Garden Party," went for $7.9 million.

The event brought in a total of $363.2 million, the auction house said.