An explosion took place in a Saudi Arabian community dominated by minority shiaon Thursday and emergency vehicles converged on the scene, a witness told AFP.
It was the latest incident in Qatif, where Islamic State group militants have carried out deadly attacks in recent years but where S discontent has also raged.
"The explosion was very huge," the witness said, asking not to be identified.
Armoured and other police vehicles sealed off the area after the explosion, the witness said.
Saudi television channel Al-Arabiya reported a car bombing was the cause of the explosion.
Video and photographs posted on social media showed a vehicle engulfed in flames in the middle of a street, with dense black smoke rising around it.
Other images showed what appeared to be at least one charred body lying beside a vehicle, which looked like an SUV, after firefighters extinguished the blaze.
The Sunni extremist IS -- which views Shia Muslims as heretics -- in 2014 began a campaign of bombings and shootings that has killed more than 40 Shias in Saudi Arabia's Eastern Province, which includes Qatif.
In August, police said they shot dead a would-be suicide bomber targeting a mosque in Qatif district.
Two months later, a gunman killed five people at a Shia meeting hall in Saihat district of Qatif.
Most of Saudi Arabia's Shia live in the oil-rich east, where they have long complained of marginalisation.
Alongside IS attacks, Shia discontent and general crime are also behind a wave of violence in the area.
In 2011, Shia protests began in the area and developed into a call for equality in the Sunni-majority Gulf country.
Police then issued a list of 23 wanted people, many of whom have since been detained or killed in shootouts.
Last month, violence escalated around a redevelopment project in the old section of Awamiya, a Qatif-area town.
The interior ministry said criminals engaged in the drug and arms trade were involved in the unrest.
A police officer was killed by a rocket-propelled grenade, following the shooting deaths of an infant and a Pakistani man, in Awamiya.