A suicide bomber on Monday attacked the Saudi city of Medina, considered the second holiest place in Islam, detonating a device close to the Prophet’s mosque.
Images obtained by the Reuters news agency showed smoke rising from the vicinity of the mosque.
Videos on social media also showed a vehicle on fire in a car park with two security officers lying nearby.
Other footage also showed ambulances and police vehicles streaming to the area.
Saudi-owned al-Arabiya TV said the bomber attacked at a time security officers were breaking their Ramadan fast.
Some reports say a young man approached the security officers who were about to break their fast to share food. He then detonated his explosives.
According to al-Arabiya, the initial death toll from the Medina attack included three suicide bombers and two security officers. There has however been no official confirmation of the death toll.
The blast followed others in Qatif and Jeddah earlier on Monday.
The explosion in Qatif, home to many minority Shia Muslims, appeared to have targeted a Shia mosque. The attacker was reportedly killed but no casualties were reported.
Two security officers were said to have been slightly injured as they tackled a suspected suicide bomber who detonated a device near the US consulate in Jeddah. The bomber died but no one else was hurt.
The mosque is the burial place of the Prophet Muhhamed and Medina is the second holiest city in Islam after Mecca.