Three suspected arsonists have been filmed lighting accelerant outside a Melbourne nightclub that was razed by fire in the middle of the night. 

One of the bumbling offenders can be seen setting alight his own arms and leg as the trio flee the building on Chapel Street, South Yarra.

The two-storey LUX Nightclub was engulfed in flames, with about 50 firefighters and 15 fire trucks called to battle the inferno about 1.50am on Thursday.

Footage has emerged showing three masked men – who are carrying red jerry cans – entering and leaving the building.

As they leave, a video obtained by the Herald Sun shows the men, dressed all in black, frantically pouring accelerant onto the footpath.

One of the suspects catches fire. Both arms and his right leg are quickly covered in flames, which he attempts to douse by stomping his feet.

Their suspicious behaviour was in full view of patrons outside a neighbouring venue.

The arms and leg of one suspect are covered in flames. Photo: Herald Sun

After the men sped away in a waiting hatchback, an inferno consumed the top floor of the LUX Nightclub.

“Within minutes of the first call, the top area of the LUX Nightclub was fully involved in fire and it was starting to come out through the roof space,” Fire Rescue Victoria’s Mitch Simons said at the scene.

A smoke warning was issued for local residents and it took crews two hours to bring the fire under control.

No one was injured as the club was closed at the time.

The blaze has been deemed suspicious, with an arson chemist to comb for clues.

“Police will investigate whether the incident is linked to any other recent incidents,” a Victoria Police spokeswoman said.

The first-floor bar has been burnt out and its roof rendered a mess of twisted metal.

The club is above a Westpac bank and boutique store, which also suffered damage.

Chapel Street was closed to traffic on Thursday morning due to the structural damage, disrupting traffic along the major road.

-with AAP