The United States has accused Iran of close involvement in attacks on commercial ships by Yemen’s Houthi rebels, alleging Tehran’s clerical state has provided drones, missiles and tactical intelligence.

The allegations, released by the White House based on US intelligence, mark the strongest remarks yet by the United States on Iran’s purported role in the attacks.

“We know that Iran was deeply involved in planning the operations against commercial vessels in the Red Sea,” National Security Council spokeswoman Adrienne Watson said.

“This is consistent with Iran’s long-term materiel support and encouragement of the Houthis’ destabilising actions in the region,” she said. “We have no reason to believe that Iran is trying to dissuade the Houthis from this reckless behavior,” she said.