The United States carried out airstrikes against five locations in Iraq and Syria on Sunday, targeting multiple weapons and munitions depots linked to Iran, two U.S. officials said.

The weapons and lethal aid stored at the sites had been used in a series of recent attacks on bases of the U.S.-led coalition fighting the Islamic State group in Iraq and Syria, the officials said.

The officials said a series of significant secondary explosions seen at the sites indicated that munitions and explosives had likely been struck. It wasn't immediately clear whether anyone was killed or injured.

There have been 11 rocket attacks against coalition bases in the last two months, including one that killed a U.S. contractor and injured four U.S. service members in Kirkuk on Friday morning, the officials said.

The coalition said coalition troops were using the base. Iraqi personnel were also wounded.

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The repeated strikes have raised concerns among U.S. military leaders, who began preparing response options earlier this month.

The officials said Iranian-backed militias with links to that country's elite Quds Force were likely behind the attacks.

Speaking to reporters Sunday at President Donald Trump's Mar-a-Lago club in Florida, Secretary of State Mike Pompeo said the airstrikes represented a "decisive response" to Iran.

"We will not stand for the Islamic Republic of Iran to take actions that put American men and women in jeopardy," he said.

Air Force F-15E Strike Eagles, pictured firing flares over the Utah Test and Training Range in July 2018, dropped precision-guided bombs in Iraq and Syria on Saturday afternoon, Defense Secretary Mark Esper said. Reuters

Defense Secretary Mark Esper briefed Trump on Saturday afternoon on the proposed military response, which included F15-Es' dropping precision-guided bombs. The strikes required presidential approval.

In a separate series of strikes, U.S. Africa Command said Sunday that it targeted two sites used by al-Shabab militants in Somalia, killing four people whom it identified as terrorists.

The announcement came one day after a truck bomb killed 78 people and injured 125 others at a security checkpoint in Mogadishu, the Somali capital.

No one has claimed responsibility in the attack, but The Associated Press reported that the Al Qaeda-linked group has often carried out similar bombings, including one in October 2017 that killed 500 people.