LONDON — A U.S. military drone was shot down over Yemen on Tuesday, according to two U.S. officials, the second such incident in Yemen in the last three months. Multiple reports state the attack took place late Tuesday.

In a separate statement, Lt. Col Earl Brown, a spokesman for U.S. Central Command, said it was "investigating reports of an attack by Iranian-backed Houthis forces on a U.S. unmanned aircraft system."

Earlier Wednesday, Houthi military spokesman, Yahya Sarea, told NBC News that fighters had downed an "armed American drone."

Sarea had earlier told the group's official Al-Masirah T.V. that their air defenses had shot down a U.S. MQ-9 aircraft.

“The air defense systems managed to shoot down an American MQ-9 aircraft with a missile in the skies above Dhamar, it struck its target accurately,” he said, according to a translation by Flashpoint, a business risk intelligence firm.

The U.S. military said a MQ-9 drone was shot down over Yemen on June 6 by what it suspects was Houthi SA-6 surface-to-air missile.

"The last US strike in Yemen was on June 24th in Al Bayda. So far this year there have been nine US strikes in Yemen. In 2018, there were 36," said a spokesperson for U.S. Central Command.

A Saudi-led coalition allied with the government has been fighting Iran-backed Houthi rebels since 2015, in support of Yemen's internationally recognized government.

The year before Houthis had taken over the capital, Sanaa, driving out the government. The four-and-a-half-year-old war has killed tens of thousands people and pushed Yemen to the brink of famine. The United Nations has called the situation in Yemen the world's worst humanitarian crisis.

Earlier this year, Congress voted to end American involvement in the Yemen war but President Donald Trump later vetoed the bill. The U.S. provides billions of dollars of arms to the Saudi-led coalition.

Explaining his veto in April Trump said the Yemen resolution was a "dangerous attempt to weaken my constitutional authorities, endangering the lives of American citizens."

In June, the United Arab Emirates, Saudi Arabia's main military ally in the conflict on the ground for most of the war, began drawing down its forces in the coalition.