A suicide bomber detonated a device near the security headquarters of Masjid-i-Nabvi in Madinah, the second-holiest site in Islam, Saudi-owned al-Arabiya television reported on Monday.
The news channel showed images of fire raging in a parking lot and reported the initial death toll in Madinah as three, which includes the suicide bomber and two security officers.
Security forces have cordoned off the area.
Al Arabiya’s correspondent said worshipers were unhurt following the attack.
All the three incidents of explosions — targeting US diplomats, Shia worshippers and the security headquarters of Masjid-i-Nabvi — follow days of mass killings claimed by the Islamic State group, in Turkey, Bangladesh and Iraq.
The attacks all seem to have been timed to coincide with the approach of Eid-ul-Fitr.
A video sent by a witness to the aftermath of the Madinah bombing showed a large blaze among parked cars in the fading evening light, with a sound of sirens in the background.
Several suicide attacks have been reported near several mosques across Saudi Arabia one-day before the end of Ramadan reports AFP.
One of the mosques targeted was the heavily populated mosque in Madina once attended by the Prophet Muhammad. So far there are no reported casualties apart from the terrorists themselves.
The wave of attacks upon Muslim populations towards the end of Ramadan is consistent with the Daesh terror network whose leader Abu Bakr al-Baghdadi has called on his followers to engage in a wave of terror to mark the Islamic holy month.
The suicide bomber was killed and two security officials were wounded.
There is no word about the nature of the blast