Saudi security forces have foiled a planned suicide attack on a mosque in the Qatif region in eastern Saudi Arabia, where many Shia Muslims live, Al-Arabiya news channel and other Saudi media reported early on Wednesday.
The Saudi-owned satellite channel said security forces killed a man who was wearing an explosive belt and arrested another.
Both men were not Saudi citizens, Al-Arabiya said.
Saudi media said the interior ministry was expected to issue a statement on the attack soon.
Saudi newspaper Asharq al-Awsat carried a similar report but said the second man was wounded after security forces exchanged fire with him.
Saudi Arabia has suffered a string of deadly shooting and bomb attacks in recent months, many of them claimed by the militant Islamic State (IS) group.
IS is bitterly hostile to Gulf Arab monarchies and is seen to be trying to stoke Sunni-Shia sectarian confrontations in Arabian peninsula states to destabilise and ultimately overthrow their dynasties.
In July, suicide bombers struck three cities across Saudi Arabia, killing at least four security officers. The apparently coordinated attacks came on the penultimate day of Ramzan.