A fire has torn through the sprawling training complex of one of Brazil's biggest football clubs, killing 10 people and leaving three teenagers injured, firefighters said.

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.

There was no word on the cause of the fire.

The ages and identities of those killed were not released but the three injured were 14, 15 and 16, the fire official said.

Beatriz Busch, the public health secretary for the state of Rio de Janeiro, said two of the injured were in stable condition and one was in critical condition. "Those who died were athletes," she added.

Local media reported that the fire started in a dormitory where youth players sleep. The fire official said that could not be confirmed.

Aerial images from Globo TV showed smoke emerging from a charred area.

Flamengo have a youth development programme for promising young players in their early teens. Many players stay at the facilities while training.

"Flamengo is in mourning," the team posted on its Twitter account.

Family members, friends and neighbours were gathering outside in hopes of getting information.

Jefferson Rodrigues, who runs a small bar near the club, said he had reached a 15-year-old player he had befriended.

"I am very happy. I just spoke to Caix Suarez and he is alive," said Mr Rodrigues, adding that the youth told him he ran when he saw the flames in the morning.

"He lost his phone, and all of his things, but the important thing is he is alive."

Joao Pedro da Cruz, a 16-year-old player in the Flamengo youth league, told the G1 news portal he had decided not to stay the night at the facility on Thursday because the team was not going to train on Friday. Instead, he went to a friend's house.

"The majority of them (the team) stayed, my friends stayed (at the facility)," he said. "Today I woke up and heard this terrible news."

Flamengo are arguably Brazil's most famous club, with an estimated 40 million fans nationwide.

Supporters are so attached to their academy team that players have a motto for them: "Flamengo makes legends at home."

Among the most famous to come through the club are Zico, a former No 10 for Brazil's national team; top goal-scorer Adriano, who rose to fame at Inter Milan; and current Real Madrid star Vinicius Jr, who not long ago was living in the structure destroyed by the fire.

As news of the fire broke, several teams and players expressed their condolences on Twitter.

"We are extremely sad and shaken by the news of the fire," tweeted Chapecoense, a team in southern Brazil that lost 22 players in a plane crash in 2016.