UNITED NATIONS, United States — United Nations experts are expected in Saudi Arabia to lead an international inquiry into the weekend attacks on oil installations in the Kingdom, diplomats said Wednesday.

"It's very good that an international probe will get under way," said one diplomat on condition of anonymity. Another source said the experts were either traveling or already in Saudi Arabia.

The UN experts have been dispatched under the terms of a Security Council resolution on the 2015 nuclear deal with Iran, and another resolution on a Yemen arms embargo, the diplomats said.

The 2015 resolution stipulates that UN experts can be sent if military hardware made in Iran are found elsewhere.

The Yemen resolution created an experts' committee on how the embargo is applied. Those experts have been activated over the Saudi attacks because the Iran-backed Houthi rebels claimed responsibility for the strikes, a diplomat said.

Riyadh said Wednesday the attacks were "unquestionably" sponsored by Iran.

Earlier, US President Donald Trump said on Wednesday he had ordered his Treasury Secretary to "substantially increase sanctions" imposed on Iran, in the wake of the attack that some US officials have blamed on Tehran.

He did not give details on the move and Tehran has denied it was behind the attack, which initially knocked out half of Saudi Arabia's oil production and sent oil prices sharply higher.

The White House and the Treasury Department did not immediately respond to requests to comment on what the sanctions could be. — AFP