Madrid said four Spanish nationals were wounded in the stabbing spree during a live performance on November 11, the first such assault since the ultra-conservative kingdom began easing decades-old restrictions on entertainment.
The Yemeni suspect took orders from an Al-Qaeda leader in Yemen, the official Al-Ekhbariya television said, as his trial began in a Saudi criminal court.
It did not reveal the source of the information or offer any other details.
Saudi Arabia is leading a military coalition supporting the Yemeni government against the Iran-backed Huthi rebels and has also been involved in the fight against Al-Qaeda.
⚡️URGENTE: Una persona acuchilla a varios actores y actrices durante una función en un teatro de Riyadh, Arabia Saudí. El momento en que se produce el ataque.pic.twitter.com/tgTLvylTs7
— Mundo en Conflicto (@MundoEConflicto) November 11, 2019
Al-Qaeda in the Arabian Peninsula (AQAP), which is active in Yemen, is considered by the United States as the most dangerous branch of the radical group.
Saudi police had earlier identified the assailant as a 33-year-old Yemeni expatriate.
An official investigation had led authorities to a second suspect, the pro-government Okaz newspaper reported on Thursday without offering any further details.
The newspaper added the Yemeni attacker sought to sow “chaos and terror” in a bid to compel authorities to stop hosting entertainment activities in the Muslim kingdom.