Riyadh: Saudi Arabia on Wednesday said that strikes on its oil infrastructure were "unquestionably" sponsored by Iran, adding that the strikes originated from the north but the exact launch site was yet to be pinned down.
It displayed what it said were fragments of the arsenal of 18 drones and seven cruise missiles that devastated two facilities in the country's east, knocking out half the kingdom's oil production.
"The attack was launched from the north and unquestionably sponsored by Iran," defence ministry spokesman Turki al-Maliki told a press conference. "We are working to know the exact launch point."
However, he would not be drawn on whether Saudi Arabia believed that Iran would ultimately be found to be the culprit, only saying they were confident they would find where the weapons were fired from.
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 on 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 Houthi 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, said 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.
"As the president said, we don't want war with anybody, but the United States is prepared," Vice President Mike Pence said in a speech in Washington on Tuesday.
The apparent hardening of the US position came as Iran's supreme leader Ayatollah Ali Khamenei ruled out negotiations with Washington "at any level". That appeared to nix remaining hopes for a dramatic meeting between President Donald Trump and his Iranian counterpart Hassan Rouhani at the United Nations next week.
Speaking to reporters on Air Force One, Trump said he too had cooled on what had always seemed to be a diplomatic long shot. "I never rule anything out, but I prefer not meeting him," Trump said.
Iran-backed Houthi rebels in Yemen, who are locked in a prolonged conflict with a Saudi-led military coalition, claimed responsibility for Saturday's oil installation attacks, which took out six percent of global supplies. But Riyadh and Washington have both ruled that out.
"Despite Iran's efforts to make it appear so" they did not originate from Yemen, Maliki said, adding the strike was beyond the capabilities of the militia -- who have however mounted dozens of smaller attacks on Saudi territory.
"The precision impact of the cruise missile indicated advance capability beyond (Iranian) proxy capacity," he said, adding that they also struck from a direction that ruled out its southern neighbour Yemen as a source.
Observers say the experience in Yemen, where despite their vast firepower, the Saudis have failed to subdue the ragtag but highly motivated militia, has made Riyadh circumspect about wading into another conflict.
"I certainly hope we're not (going to have another war)," Riyadh's ambassador to London Prince Khalid bin Bandar told the BBC in an interview. "We are trying not to react too quickly because the last thing we need is more conflict in the region."
Iran has stuck with its account that the Huthis were responsible, and Rouhani said Wednesday the rebels had done so as a "warning" about a possible wider war in response to the Saudi-led intervention in Yemen.
State media said Tehran had written to Washington through the Swiss embassy on Monday, denying any role in attacks on Saudi oil installations and warning it would respond to any action. The message "emphasised that if any actions are taken against Iran, that action will face an immediate response from Iran and its scope will not be limited to just a threat," the official IRNA news agency said.
Trump called off a retaliatory missile attack on Iran in June after the Iranians shot down a spy drone.
Trump's administration is considering responses to the latest attack, including a cyber attack or a physical strike on Iranian oil infrastructure or its Revolutionary Guards, NBC News reported, citing unnamed US officials.
Oil prices have see-sawed since the attacks, with record gains Monday followed by a tumble Tuesday as the Saudi assurances on supply soothed the markets.