Building fires are common in India due to a lack of firefighting equipment and routine disregard for safety regulations.
The fire broke out in the morning at Flourish Stay, a bed-and-breakfast in a congested neighbourhood in the south of the city, Delhi Police said in a statement.
“It is with profound sorrow that 21 persons have been declared dead in this tragic incident,” the force said.
It said search and rescue operations were continuing, with more than 40 people taken to hospitals for treatment.
Eight were in a critical condition, according to a statement by a nearby hospital where several of the injured were taken.
Indian television channels showed flames leaping from the building and thick plumes of black smoke rising into the sky.
Some 47 guests were in the hotel when the fire broke out, local lawmaker Satish Upadhyay told reporters.
Locals rushed to the site, as firefighters worked to douse the blaze and ambulances arrived to help treat the injured.
Several of those killed were visitors from African countries who had come to the city for medical treatment, the Indian Express and other local media reported.
Indian Prime Minister Narendra Modi called the incident “tragic”.
“My condolences to those who have lost their loved ones,” his office said in a statement on X.
Some reports suggested the hotel had just one door for entry and exit, and lacked proper ventilation.
“An inquiry will be conducted, and anyone who has broken norms and is responsible will be immediately arrested,” Upadhyay said.
Some people trapped on the upper floors of the building jumped onto mattresses laid out by local residents on the street outside, the Press Trust of India reported.
“People started to jump out of the building from second and third floors,” a local resident told the news agency.
The blaze was eventually brought under control with the help of eight fire engines, police said.
“All concerned agencies remain deployed at the spot to ensure every possible assistance to those affected,” the force added.
The cause of the fire was not immediately clear.
Electrical short circuits, often caused by poorly maintained wiring, remain the leading cause of fire incidents in India.
In March, a fire at a government-run hospital in eastern India killed 10 critically ill patients.
The last major fire incident in Delhi killed 43 factory workers sleeping in a building in the city’s old quarter in 2019. (AFP)
