Lady Gaga, Paul McCartney, The Rolling Stones and Beyonce took part in a global special of music, comedy and personal stories in what Gaga called a "love letter" to front-line workers battling the coronavirus pandemic.

The two-hour One World:Together at Home broadcast across multiple television channels around the world, including CBC, featured a Who's Who of pop culture, with contributions, filmed from their homes, from Elton John, Stevie Wonder, British soccer star David Beckham and former U.S. first ladies Michelle Obama and Laura Bush. Andrea Bocelli, Céline Dion, Billie Eilish and dozens of others also appeared.

"I'm so grateful for the health-care workers, the medical workers, all the grocery store workers and delivery people, the postal workers, all the other non-profits that are working so hard," Gaga said.

"This is really a true love letter to all of you all over the world, and I hope a reminder of the kindness that's occurring right now," she added.

Jimmy Fallon, centre, sings with musical group The Roots and front-line medical workers during the broadcast. (Getty Images for Global Citizen)

Hosted by three of the biggest late night television show hosts in the United States — Jimmy Kimmel, Stephen Colbert and Jimmy Fallon — the special paid tribute to teachers and health care, grocery, delivery, postal and other workers.

"We aren't asking for money tonight," said Colbert.

The event, organized by the World Health Organization (WHO) and the nonprofit group Global Citizen, was the biggest celebrity effort so far to mark the coronavirus pandemic that has killed more than 150,000 people worldwide.

It is also aimed at encouraging philanthropists and companies to contribute to the WHO's COVID-19 Solidarity Response Fund. Corporate and other donors have already contributed some $150 million US, organizers said.

"What I'd like tonight, if I can, is to give you the permission for the moment to ... smile," said Gaga, launching into a version of the ballad made famous by Nat King Cole.

Beyoncé did not perform but sent a video message in which she noted the disproportionately high death rates in the black American community due to COVID-19.

"This virus is killing black people at an alarming rate in America," she said, urging viewers to protect themselves.

6-hour live stream

The Rolling Stones, appearing in four separate locations, sang You Can't Always Get What You Want, with Mick Jagger and Keith Richards playing acoustic guitars.

Wonder, in a tribute to Bill Withers, who died two weeks ago, played Lean on Me, while McCartney, recalling that his mother was a nurse and midwife, sang Lady Madonna.

"You know the coronavirus is trouble when a Beatle gets involved," quipped Kimmel.

Earlier on Saturday, pop, classical and rap musicians from the United States, Asia and the Middle East, all performing from their homes, took part in a six-hour live stream ahead of the main event.

The live stream featured the likes of Latin star Luis Fonsi, R&B singer Jennifer Hudson, U.S. women's soccer player Megan Rapinoe, Hong Kong singer Eason Chan, India's Vishal Mishra and Emirati musician Hussain Al Jassmi.

Billie Eilish arrives at the 62nd annual Grammy Awards in Los Angeles in January. She performed for Together at Home. (Jordan Strauss/Invision/The Associated Press)

The broadcast included social media postings and news clips showing doctors and nurses being applauded by communities around the world, families greeting each other through windows, and acts of kindness in support of those who are isolated and frail.

Celebrities called on people to stay at home, wash their hands regularly, practise social distancing and put pressure on their political leaders to introduce widespread testing for the disease.