Widnes Vikings centre Kato Ottio has died at the age of 23 after suffering “a sudden health issue” in training.
Ottio joined Widnes from Canberra in December and was part of the Papua New Guinea side which lost to England in November’s World Cup quarter-finals.
He was due to travel to the UK next week in preparation for the start of the Super League season in February.
“Kato was an incredibly talented player, with a bright future,” Widnes chief executive James Rule said.
PNG Rugby Football League chairman Sandis Tsaka said Ottio had died in hospital in Port Moresby, Papua New Guinea, and further details would be released at a later stage.
Ottio won six caps for Papua New Guinea, scoring one try in four appearances to help them reach the last eight at the 2017 World Cup.
He represented his country playing volleyball before signing for Raiders in 2016, only two years after taking up rugby league.
Although he was unable to break into Canberra’s NRL side, he was a regular starter for their feeder club – the Mount Pritchard Mounties – in the New South Wales Cup.
“All of us saw at the World Cup the incredible gifts that Kato had, and his potential to forge a great career in rugby league,” Widnes head coach Denis Betts said.
“Moreover, in all of our interactions with him, we found Kato to be a person of great character, who was excited to be following his dreams.
“On behalf of the coaching team, staff and players at Widnes Vikings, I would like to offer our sincere condolences to Kato’s loved ones.”
Huddersfield centre Jordan Turner, who played with Ottio in Australia, said on Instagram: “Devastated to hear the news of Kato’s passing, some very fond memories with him from my time in Canberra.
“Legend of a bloke. Will be truly missed and was a Super League star in the making. My thoughts go out to his family. RIP Brother.”
Dave Woods, BBC rugby league correspondent
This is a devastating loss.
Ottio made a big impression in the recent World Cup. His abilities in helping PNG to the quarter-finals of that tournament had alerted a number of Super League clubs.
Widnes won the race to sign him and those close to him report how excited he was to be joining the Vikings. Widnes felt they had captured the services of a real star in the making.
The exact circumstances of his death have yet to be confirmed, but the sudden loss of a bright young talent is a devastating reminder of several recent tragedies within the game.
Rising Huddersfield star Ronan Costello died aged 17 after a freak accident, 29-year-old Wales international Danny Jones passed away after a cardiac arrest in 2015 and Wakefield’s Leon Walker died from a heart defect aged 20 in 2009.
Rugby league has a remarkable way of coming together to support family and friends in such tragic circumstances, with support channelled through its two charities – British-based Rugby League Cares and Australia’s Men of League.
Matt Newsum, BBC Sport rugby league reporter
The death of such a bright talent so young is a desperately sad shock to everyone connected with rugby league, as a fit, powerful, physical specimen of a player who seemed to have it all before him will never fulfil that promise.
There was genuine excitement about Ottio’s signing for Widnes. He was one of the success stories of Papua New Guinea’s World Cup campaign as he – along with team-mates Garry Lo, Rhyse Martin and Wellington Albert – enhanced his reputation with some fine displays.
Although he never made the breakthrough at Canberra Raiders in the NRL, there was enough to suggest from his NSW Cup and PNG exploits he would be a hit in the northern hemisphere.