Video shared on social media showed what appeared to be the plane plunging down behind a cluster of trees, followed by a large plume of black smoke.
Airline Voepass said the plane, which had taken off from Cascavel, in the state of Parana, bound for Sao Paulo’s main international airport, crashed in the town of Vinhedo, about 80 kilometres northwest of Sao Paulo.
The airline said it could not provide further information on what caused the plane, which had a PS-VPB registration, to crash.
The aircraft was listed by flight tracker FlightRadar24 as an ATR 72-500 turboprop. ATR is jointly owned by Airbus and the Italian aerospace group Leonardo.
Speaking at an event, President Luiz Inacio Lula da Silva asked for a minute of silence for the victims of the crash, adding that all on board were presumed dead.
Sao Paulo’s state fire brigade rushed seven crews to the scene of the accident, according to a post on social media.According to tracking website Flightradar24, the plane left Cascavel at 11:56 local time (14:56 GMT). The last signal received from the aircraft was about an hour and a half later.
Brazil's civil aviation agency said the plane, which was built in 2010, had been "in good operating condition, with valid registration and airworthiness certificates".
The four crew members on board at the time of the accident were all duly licensed and had valid qualifications, it added.
The Uopeccan Cancer Hospital in Cascavel told BBC Brasil that two of its trainee doctors were among the passengers who died.
The moment the passenger plane crashed was witnessed by local residents.
“When I heard the sound of the plane falling, I looked out my window at home and saw the moment it crashed," Felipe Magalhaes told Reuters news agency, adding that the sight had left him "terrified".
Another resident, Nathalie Cicari, told CNN Brasil she had been having lunch when she heard a "very loud noise very close by", describing it like the sound of a drone but "much louder".
"I went out on the balcony and saw the plane spinning. Within seconds, I realised that it was not a normal movement for a plane."
It is Brazil's worst plane crash since 2007, when a TAM Express plane crashed and burst into flames at São Paulo's Congonhas airport, killing 199 people.
President Lula paid tribute to the victims at an event where he was speaking.
“I have to be the bearer of very bad news and I would like everyone to stand up so that we can have a minute of silence," he told his audience.
He posted on social media that news of the crash was “very sad". "All my solidarity to the families and friends of the victims,” he said.
The nearby town of Valinhos sent 20 emergency personnel to the crash site as part of a joint operation, local authorities said.
"Twenty men were mobilised, including three vehicles from the Valinhos Municipal Civil Guard and one vehicle from the Civil Defense," Valinhos City Hall said in a statement.
ATR said in a statement that it had been informed of an accident involving an ATR 72-500.
"Our first thoughts are with all the individuals affected by this event," it said.
"The ATR specialists are fully engaged to support both the investigation and the customer."
