John Oliver has become the first US late-night host to address the Orlando shooting in an emotional opening to his show Last Week Tonight, which airs Sunday night in the US.

"It's still early and details are still emerging and right now this just hurts," he said. "And the worst thing is this pain is so familiar."

The satirist, whose HBO show carries a strong activist drive tackling issues such as debt-recovery, "serial liar" Donald Trump and lead poisoning, began his show with a short comment about the massacre that had taken place earlier that day.

"In Orlando early this morning the gunman attacked a Latin night at a gay club in the theme park capital. For the record, I will happily embrace a Latin night at a gay club at the theme park capital of the world as a symbol of what is truly wonderful about America."

He told viewers that the show would go ahead as normal. "It's hard to know what to do in the wake of an event like this," adding that the show would proceed with its normal intro, "jarringly inappropriate jangly music".

Lifting the tone, he cut to footage of hundreds of people queuing up around a block in Orlando to donate blood for those injured in the mass shooting.

"It kind of reminds you that that terrorist dips--t is vastly outnumbered."

Oliver has already made headlines as a powerful advocate for gun control, interviewing former prime minister John Howard in 2013 for a segment for The Daily Show with Jon Stewart. During the interview, Oliver mockingly took on the stance of the pro-gun lobby to highlight the the fact that there had been no mass shootings in Australia following the gun reforms of 1996 after the Port Arthur massacre.

"Obviously gun control doesn't work," Oliver told Howard. "It can't work, it will never work – so how was your scheme a failure?"

"Well, my scheme was not a failure," Howard replied. "We had a massacre at a place called Port Arthur 17 years ago and there have been none since."

Elsewhere, tributes continued to flood in from the entertainment world. J.K. Rowling paid tribute to a worker on the Harry Potter ride at the Universal Orlando theme park. Twenty-two year-old Luis Vielma died in the massacre. "I can't stop crying," she tweeted.

Writer-director Seth MacFarlane tweeted a strongly worded plea for gun control. "These shootings are a regular occurrence. You don't get to be shocked' anymore unless you take action to stop them. Ban automatic weapons."

Luis Vielma worked on the Harry Potter ride at Universal. He was 22 years old. I can't stop crying. #Orlando pic.twitter.com/Nz2ZCWxNsS— J.K. Rowling (@jk_rowling) June 13, 2016

It's a traumatizing & emotional time for a many people. I dream of the world reflecting on what we can do to change this violence. #Orlando— Lady Gaga (@ladygaga) June 12, 2016

These shootings are a regular occurrence. You don't get to be "shocked" anymore unless you take action to stop them. Ban automatic weapons.— Seth MacFarlane (@SethMacFarlane) June 12, 2016

There's enough hate in this world. It's just too much. Let people live their lives. Let them love. Enough hate. Let the madness end now.— Paul Feig (@paulfeig) June 12, 2016

Devastated for our friends and family in the queer community. Our hearts, our anger, our tears are for you today. pic.twitter.com/l0Yw97XcPK— Tegan and Sara (@teganandsara) June 12, 2016