Saudi defence Ministry spokesman. Colonel Turki al-Malki

Saudi Arabia on Wednesday displayed remnants of 25 drones and missiles it said were used in a crippling attack “unquestionably sponsored” by Tehran. Defence Ministry spokesman Colonel Turki al-Malki told a news conference that the attacks were launched from Iran not Yemen.

”The attack was launched from the north and unquestionably sponsored by Iran,” he said, adding Iranian Delta Wing unmanned aerial vehicles (UAV) were used in addition to cruise missiles.

An investigation into where the attacks were launched from was still under way and the result would be announced at a later date, he said.

Proof of Iranian responsibility, and in particular firm evidence that it was launched from Iranian territory, could pressure Riyadh and Washington into a response. Both nations, however, were stressing the need for caution.

Trump has said he does not want war and is coordinating with Gulf and European states.

Saudi Arabia’s Crown Prince Mohammed bin Salman said the strike was a “real test of the global will” to confront subversion of the international order.

His envoy to London, Prince Khalid bin Bander, told the BBC the attack was “almost certainly” Iranian-backed: “We’re trying not to react too quickly because the last thing we need is more conflict in the region.”

Iran dismissed the allegations. Iran again and again has denied involvement in the Sept. 14 raids, which hit the world’s biggest crude processing facility and initially knocked out half of Saudi output. Responsibility was claimed by Yemen’s Iran-aligned Houthi group.

Diplomats at the United Nations said experts were expected in the kingdom to lead an international inquiry.

US Secretary of State Mike Pompeo, who has directly blamed Iran for the strikes, was due to hold talks Wednesday with Saudi leadership as he arrived in Jeddah to weigh with the US allies a response to the strike that roiled global energy markets.

Yemen’s Iran-backed Huthi rebels, who have claimed Saturday’s strikes, vowed meanwhile they had the means to hit “dozens of targets” in the United Arab Emirates.

Saudi’s de facto leader Crown Prince Mohammed bin Salman told Russian leader Vladimir Putin in a phone call the kingdom wants an international investigation that would be seen as highly credible, the state news agency SPA reported.

President Donald Trump — who has already re-imposed sanctions that have crippled Iran’s economy — on Wednesday promised to “substantially increase” the measures, winning quick praise from Riyadh.

A US official, speaking on condition of anonymity, told AFP that the administration has concluded that the attack involved cruise missiles from Iran and that evidence would be presented at the UN General Assembly next week.

“They want to impose maximum … pressure on Iran through slander,” Iranian President Hassan Rouhani said.

“We don’t want conflict in the region … Who started the conflict?” he added, blaming Washington and its Gulf allies for the war in Yemen.

Yemen’s Houthi movement, an ally of Iran battling a Western-backed, Saudi-led coalition for more than four years, has claimed responsibility and said it used drones to assault state oil company Aramco’s sites.

The attack exposed the vulnerability of Saudi Arabia’s oil infrastructure and threw down a gauntlet to the United States, which wants to curb Tehran’s influence in the region.

U.S. Secretary of State Mike Pompeo was to meet Prince Mohammed in Jeddah on Wednesday to discuss the crisis before heading to the United Arab Emirates.

U.N. officials monitoring sanctions on Iran and Yemen were also heading to Saudi Arabia to investigate.