Pakistani authorities are searching for tens of thousands of worshippers who attended an Islamic gathering in Lahore last month just as the novel coronavirus was taking root in the impoverished nation, officials said on Saturday.

Authorities want to test or quarantine those who congregated at the Tablighi Jamaat -- an Islamic missionary movement -- from March 10 to March 12 amid fears they are now spreading COVID-19 across Pakistan and overseas.

Organisers say about 100,000 people went to the meeting, which took place despite government requests to cancel it in light of the worsening coronavirus pandemic.

Speaking on condition of anonymity, an official at Lahore's district commissioner's office said the gathering's location outside the eastern city has now been sealed off.

"Authorities in all districts (of the country) are trying to find those who have attended the event," the official said.

About 2,500 attendees -- including 1,500 foreigners -- who had remained around the event site, which includes a mosque and sleeping quarters, have been placed in quarantine.

So far, at least 154 worshippers who went to last month's Jamaat have tested positive for coronavirus, with two fatalities to date, authorities said.

Working through word of mouth and from lists of names provided by Jamaat organisers, officials have so far tracked down approximately 7,000 attendees in Punjab province and placed them in quarantine.

Tablighi Jamaat is considered one of the world's largest faith-based movements, with millions of followers, particularly in South Asia. It sends preachers to countries to spread Islam's ideals.

According to organisers, a number of foreign nationals also attended this year's gathering from countries including China, Indonesia, Nigeria, and Afghanistan. About 1,500 foreigners are now quarantined in Pakistan, but others left the country without being tested.

On March 23, Gaza's health ministry confirmed its first two cases of coronavirus were Palestinians who had attended the gathering.

Similar Tablighi Jamaat congregations were held in Malaysia and India amid the coronavirus pandemic and have been blamed for spreading the virus to other nations.

Pakistan's Science Minister Fawad Chaudhry expressed exasperation the Jamaat took place, and blamed "the stubbornness of the clergy." "Any group of people who will not adhere to the government advice and will continue to do their normal activities will become a danger to others," he said.

Senior Tablighi preacher Naeem Butt said it was "ignorant" and "irresponsible" to blame the movement for spreading the virus. "We cancelled our event after two days when the authorities told us to do so," he said.

At the time, organisers blamed rainy weather, not the virus, for ending the event. 

Coronavirus has killed at least 41 people in Pakistan, though with only limited testing available, observers worry the number is far higher.