A large fire erupted at a factory in the Indian capital killing six workers, some of whom were trapped inside and burnt beyond recognition, a fire official and reports said.

The blaze broke out at the three-storey factory, which manufactured leather bags, in a New Delhi neighbourhood on Saturday evening, a city fire department official told AFP.

"We rushed around 20 people to the hospital after evacuating them. Six of them died and seven were discharged after first aid," the official who did not give his name said.

"Seven persons are still undergoing treatment at the hospital."

Local media reports quoted witnesses as saying they saw flames leaping from the factory's windows as workers trapped inside shouted for help.

Some of the windows were blocked with iron mesh, forcing firefighters to cut their way into the building to rescue the workers, the Times of India said.

Police have taken the factory owner into custody for questioning, while an investigation was under way into the cause of the blaze, the newspaper said.

A preliminary case of causing death due to negligence had been registered against the owner, the daily said.