Hours before a pair of oil tankers were attacked in the Gulf of Oman, Iran reportedly fired a surface-to-air missile at a U.S. drone.

A U.S. official told CNN the missile missed the aircraft and landed in the water. The official said the drone observed Iranian vessels nearing the tankers prior to the Thursday attacks, but did not disclose whether the U.S. saw the vessels actually attacking the tankers.

Days before the attack, another U.S. drone was reportedly shot down in the Red Sea by a missile believed to have been fired by Iran-backed Houthi rebels. Secretary of State Mike Pompeo blamed Iran for the attack on the tankers Thursday.

“Iran is lashing out because the regime wants our successful maximum pressure campaign lifted,” Pompeo said to reporters. “The international community condemns Iran’s assault on the freedom of navigation and the targeting of innocent civilians.”

The United Kingdom, a key U.S. ally, said on Friday it also believes the attacks to have been coordinated by Iran.

Last month, four other tankers were targeted by Iran in what Pompeo described as an attempt by the country to inflate international oil prices.

The U.S. military deployed the USS Abraham Lincoln carrier strike group and a bomber task force to the Middle East. The increased military presence comes at the same time the U.S. continues to exert a “maximum pressure” campaign against the regime targeting its financial industry.