RIYADH (Reuters) - Saudi Arabia's crown prince has called for higher vigilance and better preparedness in the kingdom after a suicide attack claimed by Islamic State on a security forces mosque killed 15 people, state news agency SPA reported late on Saturday.

Thursday's attack followed two bombings in May of mosques used by the kingdom's Shi'ite Muslim minority that killed 25, several shootings of policemen in Riyadh and a car bomb outside a prison in the capital in July, all claimed by Islamic State.

The jihadist movement regards Riyadh's ruling family as having betrayed Islam through its close ties with the West, and wants to replace all Muslim states, including Saudi Arabia, with a single caliphate.

"His Highness Prince Mohammed bin Nayef bin Abdulaziz called on the need to intensify preparedness and raise the level of caution in the face of any developments that, God forbid, may arise," the official Saudi Press Agency reported. The crown prince is also interior minister.

Islamic State's leader Abu Bakr al-Baghdadi called last year for supporters in Saudi Arabia to launch their own attacks on Shi'ites, government targets and Westerners instead of traveling to Iraq or Syria to join his group.

Saudi Arabia has joined the U.S. and other Arab states in airstrikes against the group in Syria, has mobilized state-affiliated clergy to denounce the group and has detained hundreds of its suspected supporters.

Thursday's blast took place during noon prayers at the mosque in the Special Emergency Forces Centre in Abha, the capital of the southwestern Asir province, killing five members of the force, six trainees and four Bangladeshi workers.

Islamic State claimed responsibility for attacking what it called "a military camp" on Thursday and the Interior Ministry on Saturday named the bomber as 21-year-old Saudi national Yousef bin Sulaiman Abdullah al-Sulaiman.

(Reporting By Angus McDowall; Editing by Raissa Kasolowsky)