Saudi Arabia says a suicide bomber who attacked the Prophet Muhammad Mosque in the city of Medina was a young Saudi citizen with a history of drug abuse.
Twelve Pakistanis and seven Saudis have been detained in relation to the attack on Islam's second-holiest site and two others on July 4, the Saudi Interior Ministry said on July 7.
Nair al-Nujiaidi al-Balawi, 26, crossed a parking lot next to the Prophet's Mosque in Medina and detonated an explosive belt when security guards intercepted him, killing four soldiers, the ministry said.
It said three suicide bombers took part in a botched attack outside a Shi'ite mosque in Qatif, in which no civilians or police were wounded.
They were identified as Abdulrahman Salih Muhammad, Ibrahim Salih Muhammad, and Abdelkarim al-Hesni, all antigovernment activists in their early 20s.
The Medina bomber had traveled outside the country several times, most recently early this year, a ministry spokesman said on Saudi TV, adding that nitroglycerin from the blasts in Qatif, Medina, and Jeddah seemed to match, suggesting they may have been coordinated.
No group has claimed responsibility, but Islamic State militants have carried out similar bombings in the kingdom.