Saudi Arabia's official news agency says attackers have killed a border guard soldier and wounded another in Qatif, an eastern province heavily populated by the kingdom's minority Shiites.
SPA says the attack took place late on Thursday.
Friday's report identified the slain soldier as Mohammed Hazai. It gave no further details but said that authorities are investigating.
The attack came days after Saudi Arabia executed four Shiites convicted on terrorism charges for attacks on the police and their role in violent protests.
The Interior Ministry said the four were executed for incidents that took place in Qatif, home to the town of al-Awamiya, where there has been a surge in violence since May between Shiite militants and security forces who are demolishing the town's historic center.