A US military drone has been shot down over Yemen by a surface-to-air missile — the second downing of an American unmanned aerial vehicle in the country in recent months.

The MQ-9 Reaper drone was downed in Yemen’s Dhamar governate, southeast of the Houthi-controlled capital, Sanaa, on Tuesday night, two US officials told Reuters on Wednesday.

Washington believes the missile was provided to Houthi rebels by Iran, a US official told CNN, adding that it was not immediately clear if the drone was being operated by the US military or the intelligence community.

Houthi military spokesman Yahya Saria said the rocket that downed the drone “was developed locally.”

“Our skies are no longer open to violations as they once were and the coming days will see great surprises,” he added.

This is not the first time an American drone has been shot down in Yemen. In June, the US military said Houthi rebels had downed a US government-operated Reaper drone with help from Iran.

And Tehran also acknowledged earlier this year that the Revolutionary Guard Corps had shot down an American RQ-4A Global Hawk drone, insisting that it was shot down over Iranian territory. The US said the drone was in international airspace when it was brought down.

President Trump said he called off a counterstrike against Iran due to what he said would have been a high death toll.

US forces have occasionally launched airstrikes and drone attacks against Yemen’s al Qaeda branch, which has taken advantage of a four-year-old war between the Houthi movement and President Abd-Rabbu Mansour Hadi’s Saudi-backed government to try to strengthen its position in the poor country.

Tuesday’s shoot-down comes as tensions between Iran and the US have mounted since the Trump administration last year quit an international deal to curb Iran’s nuclear ambitions and began to ratchet up sanctions.

Iranian officials denounced the new penalties as “economic warfare.”

On Wednesday, Iranian Foreign Minister Mohammad Javad Zarif said Tehran may act “unpredictably” in response to the United States‘ “unpredictable” policies under Trump.

Also on Wednesday, Human Rights Watch said the Saudi-led coalition carried out at least five deadly attacks on Yemeni fishing boats last year, killing at least 47 Yemeni fishermen, including seven children.

The New York-based group added that more than 100 Yemeni fishermen are being held in Saudi Arabia, some of whom have been tortured in custody.

There was no immediate response by the coalition to the allegations by the group, which said it interviewed “survivors, witnesses, and knowledgeable sources about seven fishing boat attacks: six in 2018 and one in 2016.”

Civilians died in five attacks carried out with small arms and heavy weapons.

It said the fishermen waved white cloths, raised their hands, or otherwise showed they posed no threat. In three attacks, coalition forces did not try to rescue survivors, many of whom drowned.

The group said the Saudi-led coalition officials who ordered or carried out the attacks or tortured detainees “are most likely responsible for war crimes.”

“The naval attacks on Yemeni fishing boats make it clear that the Saudi-led coalition is not only killing civilians through countless illegal airstrikes, but also while conducting operations at sea,” said Priyanka Motaparthy, HRW’s acting emergencies director.