An attacker opened fire at a checkpoint near the Al-Salam Palace in the coastal city of Jeddah, killing two royal guards, Saudi Arabia's interior ministry said.
Three other guards were injured in the attack, which the official Saudi Press Agency attributed to a 28-year-old Saudi national who also was killed.
The attack followed three raids by Saudi security forces last week, breaking up an Islamic State cell, capturing five suspects, and killing two. Also last week, 22 people were arrested for undermining state security including the posting of videos on social media that "incite public order," SPA reported.
American citizens in Saudi Arabia were urged to exercise caution after the attack.
"Due to the possibility of ongoing police activity, American citizens are advised to exercise caution when traveling through the area," the U.S. consulate in Jeddah said.
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(Glen Carey contributed to this report.)
