Sydney - Australian rugby league club Penrith Panthers were in damage control on Monday after another lurid sex video allegedly involving players from the club surfaced on social media.

The emergence of the new tape, widely reported by Australian media, followed two similar videos on Saturday, just days after the sport's bosses introduced tough new rules following a spate of damaging off-field incidents.

One player was reportedly shown in the weekend footage and the club issued a statement to "unreservedly apologise to the club's members, fans and sponsors for the hurt and embarrassment caused by the videos and subsequent media coverage".

It has now been rocked by another video, releasing a new statement confirming it was "aware of a video allegedly involving Panthers players being circulated on social media".

"The NRL Integrity Unit is also aware of the video and the club has been assisting with their enquiries," it added.

The names of players involved in the tapes were not released.

There is no suggestion of any criminal wrongdoing, but players could face "significant" sanctions after NRL chief Todd Greenberg vowed on Friday to crack down on the sport's many scandals, including lewd videos.

It followed Canterbury Bulldogs star Dylan Napa being fined 10 percent of his 2019 salary for appearing in several sex tapes.

Greenberg described Napa's acts as "gross stupidity" but said he decided not to suspend him because the footage dated back five years and Napa had no knowledge of them being leaked.

He warned, however, that anyone appearing in videos from now on would face much harsher punishment.

"I would suggest that every NRL player would be acutely aware now that if they distribute or take video which are idiotic, senseless and juvenile and distribute them around and it gets out, they can expect a significant sanction," he said.

The latest incidents come on the back of two players being suspended indefinitely last week under a stringent new regime against NRL stars accused of serious crimes.

Under updated rules, players charged with serious criminal offences are now automatically suspended. Previously, they could continue playing while they awaited the outcome of their court cases.

St. George Illawarra's Jack de Belin, who is facing sexual assault allegations, and Manly Sea Eagles' Dylan Walker, who is accused of domestic violence, were the first to be suspended under the new rules.