Saudi Arabia displayed remnants of drones and missiles it said were used in attacks on its oil facilities as “undeniable” evidence of Iranian aggression.

The Saturday morning attacks hit a Saudi oil field and the world's largest crude oil processing plant, disrupting the kingdom's oil production.

Saudi officials showed journalists the material at a news conference on Wednesday in Riyadh, the kingdom's capital.

Saudi Defence Ministry spokesperson Col Turki al-Malki said Iranian Delta Wing unmanned aerial vehicles (UAV) were used in addition to cruise missiles.

“The attack was launched from the north and unquestionably sponsored by Iran,” he told a news conference.

The spokesperson said that “Ya Ali” cruise missiles were also launched at the two oil plants. He added that the missiles have been used by Iran's Revolutionary Guards.

Al-Maliki said the attack was “unquestionable sponsored by Iran.”

“The attack could not have originated from Yemen,” he said, disputing the claim by Yemen's Iranian-backed Houthi rebels that they launched the weapons.

A total of 25 drones and missiles were used in the attacks launched from Iran not Yemen, the ministry spokesman added.

Iran repeatedly denied being behind the attack. Tehran warned the United States it will retaliate “immediately” if Iran is targeted over the attack on Saudi oil installations, its state-run news agency reported on Wednesday, further raising Mideast tensions.

Iran's president and foreign minister also may not be able to attend next week's high-level meetings at the United Nations, as the US has yet to issue them visas, IRNA reported.

The UN meeting had been considered as an opportunity for direct talks between Iranian President Hassan Rouhani and President Donald Trump amid a summer of heightened tensions and attacks in the wake of America's unilateral withdrawal from Iran's nuclear deal with world powers a year ago.