Crews were called just after 5am to the Ninho de Urubu training ground of the Flamengo club in western Rio de Janeiro, a fire official said.
The cause of the fire is now unknown. The dormitory is known to have been home to players aged 14 to 17. All three were taken to hospital, one of them reportedly in a serious condition.
Among the most famous players to come through the club are Ronaldinho and Zico, former stars on Brazil's national team; top goalscorer Adriano, who rose to fame at Inter Milan; and current Real Madrid star Vinicius Jr, who not long ago was living in the building destroyed by the fire.
Landim addressed the media in a news conference and confirmed the 10 deaths, before vowing support for the families of the victims, many of who are yet to be confirmed, as well working with authorities to find out why the fire occurred.
Aerial images from Globo TV showed firefighters walking through a charred area with smoke emerging.
The fire broke out at 5 am in the Vargem Grande district of Rio in a modern facility where the top-flight professional Flamengo squad also trains, the news website G1 said.
After years of financial difficulties, Flamengo last year spent $6.2 million USA to expand the Ninho do Urubu training ground.
In addition to accommodation for young players, the facilities include several pitches, an aquatic park, a gym, a medical center and a mini stadium.
The Ninho do Urubu, or Vulture's Nest, gets its name from the club's symbol - a vulture.
Flamengo posted that the club "is in mourning".
Outside the complex, an AP reporter saw two ambulances and a fire truck enter.
He said: 'What sad news!
The fire follows days of heavy rains that hit the city and claimed at least six lives, leading Flamengo to close parts of its social club and cancel regular training sessions it organizes for children.
Jefferson Rodrigues, who runs a small inn near the club, said he had reached a 15-year-old player he had befriended.
Although O Globo newspaper identified at least six of the dead as youth players, the only one named by a club official was Christian Esmerio, a 15-year-old goalkeeper.
"The majority of them (the team) stayed, my friends stayed (at the facility)", he said.
- Equine flu crisis: biggest shutdown since foot and mouth hits racing
- Whitaker: I Won't Testify Unless Dems Drop Subpoena Threat
- After 2 years of rancour, Trump to call for unity in address
- National Basketball Association deadline day rumors: Pelicans send Mirotic to Milwaukee
- Bucks’ Giannis selects teammate Middleton for NBA All-Star roster
- Max is the man Hamilton fears the most, says Horner
- India vs New Zealand 2nd T20
- Rapper Wale Slams Terry Crew Over His Support For Liam Neeson
- Apple finally releases update to prevent FaceTime eavesdropping
- Uganda Adds Curvy, Sexy Women On List Of Tourism Attractions