SYDNEY (Reuters) - Australian lawmaker Bob Katter drew online complaints on Wednesday after posting a campaign video in which he shoots dead political opponents just days after a gunman killed 49 people at an Orlando gay nightclub.

The video, uploaded to his social media channels, features two men wearing shirts for Australia's major political parties, the conservative Liberal Party and center-left Labor Party, putting up an "Australia for sale" placard.

Seconds later the video cuts to a smiling Katter, blowing smoke from the barrel of a gun as the camera pans down to the two men apparently lying dead on the ground.

But the timing of the ad, just three days after gunman Omar Mateen shot dead 49 people in the worst mass shooting in modern U.S. history, drew sharp rebukes on social media.

Katter, whose minor Katter's Australia Party focuses on issues related to rural Australia, denied that he was attempting to be deliberately controversial with the video. Australia is set to hold national elections on July 2.

"I'm not giving an explanation. You can go and watch the advertisement because it's an anti-selling off Australia advertisement," he told the Australian Broadcasting Corp.

"It was just for humor value. But it was humor getting a message across."

That argument did not seem to gain much traction on Twitter, where users savaged Katter.

"Wouldn't be a real election without Katter doing something weird or borderline insane," Twitter user Samuel McAuliffe wrote.

"So Bob Katter decides that now would be a really good time to release a video showing him shooting people dead," tweeted @GordonlKnight.

(Reporting by Matt Siegel; Editing by Nick Macfie)