DUBAI, United Arab Emirates (AP) – Despite a month of U.S.-led airstrikes, Yemen’s Iran-backed Houthi rebels remain capable of launching significant attacks. This week, they seriously damaged a ship in a crucial strait and downed an American drone worth tens of millions of dollars.

The continued assaults by the Houthis on shipping through the crucial Red Sea corridor—the Bab el-Mandeb Strait—against the backdrop of Israel’s war on Hamas in the Gaza Strip underscore the challenges in trying to stop the guerrilla-style attacks they have used to hold onto Yemen’s capital and much of the war-ravaged country’s north since 2014.

The campaign has boosted the rebels’ standing in the Arab world, despite their human rights abuses in a yearslong stalemated war with several of America’s allies in the region. Analysts warn that the longer the Houthis’ attacks go on, the greater the risk that disruptions to international shipping will begin to weigh on the global economy.

On Monday, both the Houthis and Western officials acknowledged one of the most serious attacks on shipping launched by the rebels. The Houthis targeted the Belize-flagged bulk carrier Rubymar with two anti-ship ballistic missiles, and one struck the vessel, the U.S. military’s Central Command said.

The Rubymar, which reported problems with its propulsion in November, apparently became inoperable, forcing her crew to abandon the vessel.

Houthi military spokesman Brigadier General Yahya Saree claimed on Monday night that the Rubymar sank. However, satellite images from Planet Labs PBC analyzed by The Associated Press showed the Rubymar still afloat at 2 p.m. local time Tuesday just north of the Bab el-Mandeb. A large oil slick trailed the vessel.

The Rubymar attack marked one of a few direct, serious hits by the Houthi rebels on shipping. In late January, another direct hit set a Marshall Islands-flagged tanker ablaze for hours.

Meanwhile, the Houthis early Tuesday released footage of what they described as a surface-to-air missile bringing down a U.S. MQ-9 Reaper drone off the coast of Hodeida, a Yemeni port city they hold on the Red Sea. The footage included a video of men dragging pieces of debris from the water onto a beach.

Images of the debris, which included writing in English and what seemed to be electrical equipment, appeared to correspond to known pieces of the Reaper, usually used in attack missions and surveillance flights. Pentagon spokeswoman Sabrina Singh told journalists in a briefing the Houthis shot down the drone.

In November, the Pentagon acknowledged the loss of an MQ-9, also shot down by the rebels over the Red Sea.

Since the Houthis seized the country’s north and its capital of Sanaa in 2014, the U.S. military has lost at least four drones to shootdowns by the rebels—in 2017, 2019 and this year.

Meanwhile, the Houthis claimed an attack on the Sea Champion, a Greek-flagged, U.S.-owned bulk carrier full of grain bound for Aden, Yemen, carrying grain from Argentina. Central Command said the carrier “has delivered humanitarian aid to Yemen 11 times in the past five years” as the country remains on the edge of famine amid the war there.

The rebels separately claimed an attack on the Marshall Islands-flagged bulk carrier Navis Fortuna, a ship that had been broadcasting its destination as Italy with an “all Chinese” crew to avoid being targeted. Private security firm Ambrey reported that the vessel sustained minor damage in a drone attack.

The U.S. shot down 10 bomb-carrying Houthi drones, as well as a cruise missile heading toward the Arleigh Burke-class destroyer USS Laboon over the last day, Central Command said Tuesday. The U.S. military also conducted strikes targeting a Houthi surface-to-air missile launcher and a drone prior to its launch.

The Houthis acknowledged the drone attacks and claimed other assaults not immediately acknowledged by the West.

Since November, the rebels have repeatedly targeted ships in the Red Sea and surrounding waters over Israel’s war against Hamas in the Gaza Strip. They have frequently targeted vessels with tenuous or no clear links to Israel, imperiling shipping in a key route for trade among Asia, the Mideast and Europe. Those vessels have included at least one with cargo for Iran, the Houthis’ main benefactor.

The European Union has launched its own campaign to protect shipping, with member France saying on Tuesday that it shot down two Houthi drones overnight in the Red Sea.

So far, no U.S. sailor or pilot has been wounded by the Houthis since America launched its airstrikes targeting the rebels in January. However, the U.S. continues to lose drones worth tens of millions of dollars and fire million-dollar cruise missiles to counter the Houthis, who are using far cheaper weapons that experts believe largely have been supplied by Iran.

Based on U.S. military statements, American and allied forces have destroyed at least 73 missiles of different types before they were launched, as well as 17 drones, 13 bomb-laden drone boats and one underwater explosive drone over their monthlong campaign, according to an AP tally. Those figures do not include the initial January 11 joint U.S.-UK strikes that began the campaign. The American military also has shot down dozens of missiles and drones already airborne since November.

The Houthis have not offered much information regarding their losses, though they have acknowledged at least 22 of their fighters have been killed in the American-led strikes. Insurgent forces including the Houthis and allied tribes in Yemen number around 20,000 fighters, according to the International Institute for Strategic Studies. They can operate in small units away from military bases, making targeting them more difficult.

The Houthis may view the costs as balanced by their sudden fame within an Arab world enraged by the killing of women and civilians by Israel in Gaza.

In the past, others—including the late Iraqi dictator Saddam Hussein and al-Qaida leader Osama bin Laden—have used the Palestinians’ plight to justify their “actions and garner support,” wrote Fatima Abo Alasrar, a scholar at the Washington-based Middle East Institute.

“It legitimizes the Houthis’ actions in the eyes of those who sympathize with the Palestinian cause, distracts from the more immediate issues associated with the Yemen conflict and the failures of Houthi governance, and potentially broadens the base of their support beyond Yemen’s borders,” Ms. Alasrar added.

If the Houthi attacks continue, it could force the U.S. to intensify and widen its counterattacks across an already volatile Mideast.

“Without a cease-fire in Gaza, the Houthis could be tempted to further escalate against U.S. interests in the Red Sea and in the region,” wrote Eleonora Ardemagni, a fellow at the Italian Institute for International Political Studies.

For Washington, “deterrence options” are getting narrower, she added.