TEHRAN, Iran (AP) — Iran’s Revolutionary Guard shot down a U.S. drone on Thursday amid heightened tensions between Tehran and Washington over its collapsing nuclear deal with world powers, American and Iranian officials said, though they disputed the circumstances of the incident.

The Guard said it shot down the drone over Iranian airspace, while two U.S. officials told The Associated Press that the downing happened over international airspace in the Strait of Hormuz. The different accounts could not be immediately reconciled.

Previously, the U.S. military alleged that Iran had fired a missile at another drone last week that was responding to the attack on two oil tankers near the Gulf of Oman. The U.S. blames Iran for the attack on the ships; Tehran denies it was involved.

The attacks come against the backdrop of heightened tensions between the U.S. and Iran following President Donald Trump’s decision to withdraw from Tehran’s nuclear deal a year ago.

Separately, Saudi Arabia said on Thursday that Yemen’s Iranian-allied Houthi rebels launched a rocket targeting a desalination plant in the kingdom the previous night. The White House said Trump was briefed about that attack.

Iran has quadrupled its production of low-enriched uranium and threatened to boost its enrichment closer to weapons-grade levels, trying to pressure Europe for new terms to the 2015 nuclear deal.