At least 43 people were killed on Sunday in a devastating fire that ripped through a bag factory in the congested old quarter of the Indian capital New Delhi, with survivors describing the screams of workers trapped inside.

Police and fire officials said they had rescued at least 58 people and did not expect to find more bodies.

The blaze was the worst in Delhi since 59 movie-goers died in a cinema in 1997.

The cause of the blaze is not yet known, but the city's poor planning and lax enforcement of building and safety codes have often been blamed for such deadly incidents.

The building's owner and manager were arrested on Sunday, police told the Press Trust of India news agency.

Tearful relatives spoke of receiving desperate calls from factory workers begging to be saved from the inferno in the poorly lit premises in the commercial hub of Sadar Bazar. The fire started around 05:00 (23:30 GMT Saturday).

A man named Musharaff who was trapped inside the four-storey structure made a desperate phone call to ask that his children be looked after.

"Monu, brother, I am going to die today," he said in the recording of a call played by the ABP Hindi language news channel.

"Please take care of my kids. I can't breathe. There are so many others here. Just can't breathe," he kept repeating in Hindi, before finally breaking down.

Authorities said they do not know if Musharaff was among the survivors.

One man who did survive, Sabi Abbas, told AFP he had just finished work and was about to go to sleep in the factory's modest sleeping quarters when he heard screams from the third floor.

"I rushed to the floor and saw the wires were dangling and on fire as acrid smoke filled up the corridor," he said, adding that he ran out of the building with his wife and daughters.

Such factories often provide sleeping quarters for poor workers, mostly migrant, who save money by bedding down at their workplaces.

Suffocated

The building was home to several manufacturing units producing items including schoolbags and packing materials, which fuelled the spread of the blaze, officials said.

Prime Minister Narendra Modi tweeted that the fire was "extremely horrific".

Authorities promised they would provide financial assistance to victims' families and survivors.

Locals said the factory, which also made purses and jackets, had just one entrance; 20 rooms on each floor were connected by a single internal stairway.

"Most of the casualties happened because of suffocation," witness Mohammed Khalil told AFP.

"After the fire, people didn't have any way to get out, and I believe many were asleep and because of the smoke, they got suffocated."

Others told AFP they believed the fire started on the first floor, sparked by exposed wires, before spreading to an area where foam and plastic chairs were stored.

Anxious relatives and friends gathered outside a nearby hospital morgue to identify the bodies.

Naushad Ahmad was looking desperately for a missing friend, whom he was unable to reach on his mobile phone.

"I have been to the factory and this tragedy was waiting to happen," he told AFP.

"There was only one exit and entrance to the building... People didn't get a chance to escape."

Dozens rescued

After searching for his father-in-law and brother-in-law for two hours, Sajjamuddin Ahmad discovered they were dead, he told AFP.

Families of the victims said they were mostly migrant workers from Bihar, one of India's most impoverished states. Some of them were paid just 1,000 rupees ($14) a month, they said.

The site had been operating without required fire safety clearances, Delhi's fire services director told the Press Trust of India.

The news agency also said that more than 150 firefighters battled for nearly five hours to put out the blaze.

Factories and small manufacturing units in big Indian cities are often located in old, cramped areas, where the cost of land is cheaper.

The blaze was the latest in a series of fire tragedies to hit India in recent years.

In 2016, more than 100 people were killed after a massive explosion during a banned fireworks display in the southern state of Kerala.

In 2011, at least 90 patients died after a fire in a Kolkata hospital. In 2004, 94 children burned to death in a fire at a school in Kumbakonam in the southern state of Tamil Nadu.

In January 2018, 17 workers were killed after a blaze in a plastic manufacturing facility in New Delhi.