Saudi Interior Ministry revealed on Saturday the suicide bomber of a Shiite mosque in the eastern city of Qatif is called Abdel Rahman Qashamy, adding the assailant used RDX explosives, Al-Arabeya news channel reported. Qashamy, whose age has not been revealed, bombed himself Friday inside a Shiite mosque in Qatif as worshippers were commemorating the 7th century birth of a revered figure, residents and officials said. Loyalists of the extremist Islamic State of Iraq and Syria (ISIS) claimed responsibility for the attack - the second against Shiites in the kingdom in six months. In November, the extremist ISIS group was accused of being behind the shooting and killing of eight worshippers in the eastern Saudi Arabian village of al-Ahsa. Despite a string of ISIS-related attacks over the past several months that have also targeted police, Friday's suicide bombing appears to be the deadliest in the country in nearly a decade. Habib Mahmoud, managing editor for the state-linked Al-Sharq newspaper in Qatif, said that the local Red Crescent authorities confirmed to him that 19 people had been killed and 28 wounded. Al Arabiya News Channel reported Friday that 21 have been killed, and 81 wounded.