Beijing - Cheick Tiote's Chinese club said the cause of his death was still under investigation on Tuesday after the Ivory Coast international collapsed in training and died.
Tributes poured in for the former Newcastle United midfielder, who moved to China's second-tier Beijing Enterprises in February after seven years in England's north-east.
Beijing Enterprises described how Tiote, 30, "suddenly fainted" during training on Monday and was rushed to hospital, where he died.
The club's general manager Yang Junsheng told reporters that authorities were still trying to determine the cause of death.
"We will remember the spirit that he brought us and his football ideals," Yang added.
As fellow players paid tribute to the popular, hard-tackling midfielder, a group of fans laid a bouquet of white flowers on the pitch at Beijing's National Olympic Sports Centre stadium.
Ivory Coast team-mate Gervinho, who plays for China's Hebei China Fortune, described Tiote as a "warrior" and a "champion".
"May your soul rest in peace," he said on Twitter.
Brazil's Oscar, now at Shanghai SIPG after moving from Chelsea, tweeted: "Rest in peace, Cheick Tiote. My family prays for your family."
Tiote was well known in English football circles after his stint with Newcastle, including six Premier League campaigns before their relegation last year.
He is perhaps best remembered for his crunching left-foot volley from 25 yards to secure a 4-4 draw with Arsenal in 2011.
Tiote was also part of the Ivory Coast squad that delivered the 2015 Africa Cup of Nations after a 23-year drought.
Earlier this year he became one of a number of players - including several high-profile, lavishly paid acquisitions - to move to Chinese teams.
Several footballers have died in similar circumstances including Cameroon's Marc-Vivien Foe, who collapsed during a Confederations Cup match in 2003 and died from a previously undiagnosed heart condition.
Newcastle said in a statement that they were "devastated" about Tiote while Alan Pardew, who managed him at Newcastle, said he "loved" the player.
"From the moment I arrived at Newcastle, Cheick was a wonderful presence around the dressing room and his performances on the field often defied belief," Pardew said in a statement, quoted by independent.ie.
"I loved him. He's everything that you want in a Newcastle player."
Tiote was capped 52 times by Ivory Coast and was in their squads for both the 2010 and 2014 World Cups.
He began his European club career with Belgian outfit Anderlecht and had a loan spell at Roda JC Kerkrade before moving to FC Twente in 2008.
Tiote signed for Newcastle in 2010 and made 156 appearances for the club, becoming a favourite with fans.
"The thoughts of everyone at Newcastle United are with Cheick's family, friends, team-mates and everyone connected with the clubs he represented," a club statement said.
Chinese fans also expressed their sorrow over Tiote, who grew up in poverty as one of 10 children and didn't own a pair of football boots until he was 15.
"I hope there is football in heaven," said one user on China's Twitter-like Weibo.
Another said: "Although I'm not a fan of Beijing Enterprises club, we are both people who love football and I feel sorry for him."
Rival club Tianjin Quanjian also expressed "its deep condolences", while Shanghai SIPG said it was in "mourning" over the talented player's death.