At least 21 people have been killed and many others injured after a fire tore through a multi-storey building in south Delhi, police in India's capital say.

Many of the victims were foreigners - including people from South Asian and African countries - who had travelled to India for medical treatment or to accompany relatives undergoing care, local media reported.

The building in the Malviya Nagar area allegedly operated as a bed-and-breakfast catering to patients and relatives of those receiving treatment at a nearby private hospital.

More than 40 people were rescued and taken to hospital. It remains unclear how many were inside the building when fire broke out. Its cause is not yet known.

The blaze is one of the deadliest in recent years in the Indian capital.

"The fire was brought under control quite early on - it was contained very quickly. We have now cleared the building and opened it up for the police," fire officer AK Malik said.

Delhi minister Ashish Sood said authorities were investigating whether the building had the necessary permissions to operate as a bed-and-breakfast facility, adding that those found responsible for any violations would face criminal action.

Prime Minister Narendra Modi expressed his condolences and announced compensation of 200,000 rupees ($2,088; £1,552) for the families of those killed and 50,000 rupees for those injured.

Videos on social media showed flames shooting from the building as people gathered nearby. Footage broadcast by Indian news channels showed its exterior badly charred as emergency workers searched the site.

Eyewitnesses and locals at the scene told BBC Hindi that, upon entering the building, they found many people unconscious - some lying beneath beds in hotel rooms and others collapsed in washrooms.

Wasim, who lives nearby and was among the first responders at the scene, recounted a particularly shocking incident. He said he found bodies of a couple in a washroom, holding each other in an embrace.

Another witness said they performed CPR on several unconscious victims and managed to revive some of them.

A shopkeeper who runs a quilt store opposite the building said he spread quilts on the ground below to cushion people attempting to jump to safety.

Several people jumped from the upper floors and some survived, he said.

Authorities have not yet released a full list of those killed or formally identified the victims. Local media reports, citing officials and other sources, said some of the victims were foreign nationals, including people from neighbouring South Asian countries as well as countries in Africa and Central Asia.

Several people in the building were from Bangladesh and other parts of South Asia and had travelled to Delhi for medical treatment, local lawmaker Satish Upadhyay said.

By early evening, the search and rescue operation was nearly complete but ambulances are still on standby as officials continue clearing debris from the site.

Fires are common in India, where building safety laws are often poorly enforced.

From factories and coaching centres to hospitals and entertainment venues, many of Delhi's deadliest blazes have exposed a persistent gap between safety rules on paper and their implementation on the ground.

Investigations have repeatedly pointed to lax inspections, faulty electrical systems and buildings operating beyond their approved use.