Saudi Arabia's King Abdullah arrived in Jeddah from Casablanca on Friday, having cut short a private holiday in Morocco, the state news agency said.
The elderly king returned early because of "repercussions of the events that the region is currently witnessing," the agency said, in an apparent reference to Syria.
Saudi Arabia has been a major financial patron of rebels fighting to oust Syrian President Bashar al-Assad.
After months of deliberation, U.S. President Barack Obama's administration said on Thursday it would now arm Syrian rebels, having obtained proof the Syrian government used chemical weapons against them.
The movements and health of senior royals in Saudi Arabia, the world's top oil exporter, are closely watched because of their immense executive power.
The Saudi king, who turned 90 this year, had an operation in November, one of several in recent years, which kept him in hospital for nearly a month.
He was shown on Saudi television this week after chairing a Cabinet meeting for the first time in months.