Saudi authorities have arrested nine American citizens among 33 “terror” suspects rounded up over the past days, the Saudi Gazette newspaper reported on Sunday.

Four Americans were arrested on Monday and five others over the past four days, the paper reported citing an unidentified source.

The arrests also included 14 Saudis, three Yemenis, two Syrians, an Indonesian, a Filipino, an Emirati, a Kazakhstan national and a Palestinian, the paper said.

It did not say if any of the “terror suspects” was linked to the Islamic State group, which has claimed several deadly attacks against security forces and Shiites in the kingdom in recent months.

On Friday, a suicide bomber attacked a Shiite mosque in Eastern Province killing four people before worshippers disarmed and tied up his accomplice who had fired on them.

IS, a radical Sunni group that considers Shiites heretics, did not claim that attack.

The Saudi Gazette said some 532 IS suspects accused of plotting attacks in the kingdom are being questioned ahead of their trial at the criminal court in Riyadh.

They are members of six cells arrested in “pre-emptive” raids across the kingdom and include a Saudi woman and a Filipina, the paper said.

Also on Sunday, the Saudi interior ministry said they were searching for nine suspects allegedly involved in an August suicide bombing that targeted a mosque inside a police headquarters, killing 15 people.

IS had claimed the attack in the southern city of Abha.

The ministry said in a statement that three other suspects, including a member of the kingdom's special forces, had been arrested in connection with the Abha mosque bombing.

The oil-rich kingdom offered rewards between one million riyals ($276,000) and seven million riyals ($1.87 million) for anyone who helps in the arrest of a suspect or thwarts an attack. (AFP)

•Photo courtesy of AF /Fayez Nureldine shows members of a Saudi special police unit.