Reports coming out of Saudi Arabia suggest that tens of people have also been wounded in the attack.
A thick smoke was seen billowing from the city. The Saudi security forces have also blocked off the hospital in al-Qadih district, preventing the patients and the injured from receiving medical treatment, Saudi opposition activists said.
It is not immediately clear what has been behind the violent military operation.
The area has already been simmering with tensions after a Saudi court sentenced a senior anti-regime cleric to death.
On 15 October 2014, Shiite cleric Sheikh Nemir al-Nimr was sentenced to death by the Specialized Criminal Court for "seeking 'foreign meddling' in Saudi Arabia, 'disobeying' its rulers and taking up arms against the security forces. His brother, Mohammad al-Nimr, was arrested on the same day for tweeting information about the death sentence.
In November, Sheikh Nimr lodged a formal complaint against the verdict and the case will be referred to an appeal court, in which five judges will decide on the death sentence, Alriyadh newspaper reported.
In reaction to the controversial sentence, people took to streets in the city of Qatif in Eastern Province to condemn the move.
Since February 2011, protesters have held demonstrations on an almost regular basis in Saudi Arabia, mainly in Qatif and Awamiyah in Eastern Province, despite a deadly crackdown by the regime.
The protesters primarily demand the release of all political prisoners, freedom of expression and assembly, as well as an end to widespread discrimination.