Security officials, speaking on condition of anonymity, said the shootout began on Monday just before 2pm local time (1100 GMT), and may involve Islamist fighters.
Helicopters were assisting from overhead, they said. They did not provide any further details.
Buraida is 340km northwest of Riyadh, the capital. It is in the same region where police killed four wanted fighters last week in clashes that also left two police officers dead.
In recent weeks, the number of confrontations between Saudi security forces and fighters has increased.
Saudi Arabia had launched a high-profile crackdown on fighters after attacks on Riyadh housing compounds in May and November 2003. The government said it had foiled dozens of attacks in the kingdom. Most of the attacks were blamed on al-Qaida.
The most recent attack in Saudi Arabia targeted the offices of Houston-based ABB Lummus Global Inc in the western city of Yanbu on 1 May, killing six Westerners and a Saudi.
In April, attackers bombed a security building in Riyadh, killing five people and injuring 148 more.