At least 18 people died and nearly 50 were injured in a stampede in Mumbai early on Saturday as thousands of mourners gathered following the death of the 102-year-old leader of a Muslim sect, police said.

The stampede took place outside the home of Syedna Mohammed Burhanuddin, the spiritual leader of the Dawoodi Bohra Muslim community, in Malabar Hill, a wealthy part of the city.

He died on Friday and his body had been placed in his home to allow followers to pay their respects.

Witnesses said a large crowd of mourners was pressed against the gates of the house at the time of the stampede.

"There were a lot of people pouring in, and there was not much attention given by the government and the police, who should have been here and who should have managed things," said one man wearing traditional white flowing Bohra Muslim attire.

Mumbai police commissioner Satyapal Singh said neither police nor organisers had expected such a large number of mourners.

Several of the injured were released after treatment at nearby hospitals, said a city official who declined to be named as he was not authorised to speak to the media.

Later on Saturday, tens of thousands of people lined narrow streets along the route of the funeral procession as it headed towards a mausoleum in south Mumbai where the leader will be buried alongside his father.

"People have come from outside India, and more will keep coming. Everyone was very fond of him," said 62-year-old Mumbai-resident Juzer Lokhandwala, who attended with his family to pay their last respects.

The origins of the Shia Muslim sect can be traced to Yemen. In India, some of the largest Bohra Muslim communities live in the western state of Gujarat, where many are merchants.

The community, widely seen as mostly prosperous and philanthropic, runs a large speciality hospital in Mumbai.

Stampedes frequently happen at religious sites in India but they are rare in large cities, such as Mumbai, where there is a greater police presence to monitor the flow of people.

Last October, about 115 people were killed in a stampede at a Hindu temple in the central state of Madhya Pradesh.-Reuters