A helicopter from the HMS Montrose frigate spotted speedboats moving away from the Iranian coast on Jan 28 and Feb 25 and dozens of packages containing the advanced weaponry were confiscated, the Royal Navy said in a statement.

“The seized packages were returned to the UK for technical analysis which revealed that the shipment contained multiple rocket engines for the Iranian-produced 351 land attack cruise missile and a batch of 358 surface-to-air missiles,” it added.

It did not say where the missiles were bound, but said the 351 cruise missile, with a range of 1,000 km (620 miles), is often used by Yemen’s Houthi group to target Saudi Arabia and the United Arab Emirates.

The US navy destroyer USS Gridley supported the February seizure, the Royal Navy said. Both seizures occurred while HMS Montrose was on routine maritime security operations, it added.

“This action demonstrates that we will not allow irresponsible and aggressive acts by Iran to go unchecked on land, sea and air,” US central command spokesperson Colonel Joseph Buccino said in a statement.

The Iranian government did not immediately respond to a request for comment. Houthi officials were not immediately available to comment.

Riyadh and Abu Dhabi have been at war with the Iran-aligned Houthis since 2015, in a conflict widely seen as a proxy war between the two Western-backed Arab Gulf states and Iran.