More than 125 firefighters battle blaze at London's Somerset House

More than 125 firefighters have been involved in battling a blaze at London's Somerset House, a large arts venue that contains priceless works by Monet, Cezanne and Van Gogh.

Heavy smoke and flames that could be seen coming from the roof about noon on Saturday (9pm on Saturday AEST) had died down a few hours later as firefighters poured water on it from the buckets on ladder trucks.

"Crews are tackling flames located in part of the building's roof," the London Fire Brigade said.

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"Two of the Brigade's 32m ladders have been sent to the scene to support firefighting operations.

"The entire site at Somerset House is now closed to the public whilst we tackle the fire.

"Traffic in the surrounding area will be impacted as crews respond."

It appeared from video footage that flames had burned a hole in the roof of the building located next to the River Thames.

The cause of the fire was not yet known, the London Fire Brigade said.

The first call about the fire was received at 11.59am on Saturday (9pm AEST).

The number of crews continued to rise - initially the fire brigade said it was 10 fire engines and 70 firefighters and that later increased to 20 fire engines and about 125 firefighters.

Somerset House said staff and the public were safe and artworks were not in the area of the fire. The venue had been scheduled to host a breakdancing event.

"A fire was spotted at about midday in one corner of the west wing, the site was immediately evacuated and the London Fire Brigade called, who arrived very quickly," Jonathan Reekie, director of Somerset House Trust, said.

"The west wing is mainly offices and back-of-house facilities, there are no artworks in that area."

Somerset House is an iconic building on the Strand, near to the Australian High Commission, and at its southern end overlooks the River Thames.

The fire was on the opposite side of the large complex from The Courtauld Gallery that features works such as Vincent Van Gogh's Self-Portrait with Bandaged Ear and The Descent From The Cross by Peter Paul Rubens.

The neoclassical building was reconstructed almost 250 years ago after the original Somerset House was demolished after being neglected.

The original palace was built in 1547 by Edward Seymour, Duke of Somerset, who was later executed at the Tower of London.

Queen Elizabeth I lived in the palace as a princess for five years before ascending to the throne.

It was later demolished and rebuilt in the 1700s.

In 1604, the Treaty of London was signed within the building, ending the 19-year Anglo-Spanish War.

Somerset House is now the host of creative events and exhibitions. On Saturday, it said a dance battle was supposed to be held in the building's open air courtyard, with "a day of dance and breaking showcases, workshops, live DJs and a big outdoor party, all culminating in a head-to-head dance battle between the four corners of London".

- Reported with CNN and Associated Press