LONDON (GUARDIAN) - UFC star Conor McGregor said on Tuesday that he has "decided to retire young". The UFC featherweight champion, who lost by second-round submission to Nate Diaz in a non-title fight last month, made the abrupt, cryptic announcement on his verified Twitter account.

"I have decided to retire young. Thanks for the cheese. Catch ya's later." He tweeted.

Extraordinarily, Diaz also then announced he was also giving up the sport.

"I guess my work here is done I'm retiring too," he tweeted.

The strange development prompted some online to speculate that the retirements were a publicity stunt.

Irishman McGregor, 27, who has emerged as the sport's biggest draw, had already agreed to a rematch with Diaz at UFC 200 on July 9.

But others said the retirements, especially McGregor's, could be because of Joao Carvalho's recent death.

The announcement comes one week after the death of Carvalho from injuries suffered during a Total Extreme Fighting card earlier this month where McGregor watched from ringside.

McGregor called Carvalho "a hell of a fighter" in a Facebook post following his passing, adding: "To see a young man doing what he loves, competing for a chance at a better life, and then to have it taken away is truly heartbreaking.