Customers were trapped inside after a huge fire broke out (Picture: @EmergenciasMad/Twitter)

Two people have died and at least 12 others were injured after a waiter set a pizza alight in front of diners, reports say.

The deadly blaze broke out at an Italian restaurant in Madrid and is believed to have been started by the waiter flambéing a meal as it was served.

A flambé is a cooking technique where food is doused in alcohol and ignited to create a burst of flames.

It’s reportedly a specialty of the Burro Canaglia Bar and Resto in the Salamanca district of the Spanish capital, where the fatal incident happened on Friday night.

Carlos Marin, a Madrid fire service night supervisor, said customers were stuck inside with no way out after flames engulfed the diner and spread rapidly through the roof, reports CNN.

In a video tweeted by Madrid city emergency services, he said: ‘The restaurant had just one exit, and since the fire was very close to the door, people went back to the rear of the restaurant, and they were completely trapped.’

Six of those injured in the fire are in a serious condition in hospital, according to the city’s emergency information office.

Two people were killed in the fire in Madrid (Picture: Reuters)

Six people are in a serious condition in hospital (Picture: @EmergenciasMad/Twitter)

Madrid mayor Jose Luis Martinez Almeida told reporters at the scene that one restaurant employee and one of the customers were killed.

He told Spain’s state television TVE: ‘It appears the fire started when a flambéed pizza was being served, which set fire to the decorations in the restaurant.

‘Firefighters told me it was a ferocious fire in the way it started and the smoke it generated, and if the fire station wasn’t just 100 metres away, the number of fatalities could have been higher.’

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Eyewitnesses reported seeing the flames quickly spread up the walls and ceilings as emergency services battled to rescue those inside.

Spanish police are investigating the cause of the fire.

Earlier this month, a 15-year-old schoolgirl was tragically killed in an ‘arson attack’ at a block of flats in London.

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Customers were ‘completely trapped’ inside after flames engulfed the restaurant.