India and Pakistan sealed off centres belonging to a Muslim missionary group on Tuesday and began investigating how many coronavirus cases were linked to its activities.

Tablighi Jamaat is a Deobandi Sunni Muslim missionary movement that preaches worldwide. Every year, tens of thousands attend its congregations in the Pakistani city of Lahore and other parts of South Asia.

New Delhi's city administration has flagged a Muslim quarter where the 100-year-old Tablighi group has a branch as a coronavirus hotspot after dozens of people tested positive for the virus there and at least seven died.

Authorities said people kept visiting the centre, in a five-storey building in a neighbourhood of narrow, winding lanes, from other parts of the country and abroad, and that it had preached sermons to large groups despite government orders on social distancing.

Hundreds of people were crammed into the building until the weekend, when authorities began taking them out for testing. More buses arrived on Tuesday to take them away to quarantine centres in another part of the city.

"It looks like social distancing and quarantine protocols were not practised here," the city administration said in a statement.

"The administrators violated these conditions and several cases of corona-positive patients have been found ... By this gross act of negligence, many lives have been endangered ... This is nothing but a criminal act."

Authorities are trying to trace the movements of people who had gathered at the Tablighi centres in Delhi and Lahore and the people who were exposed to them. 

In Pakistan, the Lahore Tablighi centre was sealed off and dozens of other preaching centres across the country were placed in quarantine after 143 Tablighi members tested positive and three died, officials said. Media said the cases included Tablighi members from Malaysia, Indonesia, Thailand, Nepal, Myanmar, Kyrgyzstan and Saudi Arabia.

Musharraf Ali, an administrator of the Tablighi centre in Delhi, said the group had been seeking help from police and the city authorities to deal with the large number who were unable to leave after the government announced a lockdown.

"There was no option ... but to accommodate the stranded visitors with prescribed medical precautions until such time as the situation becomes conducive for their movement or arrangements are made by the authorities," Ali said.