(Bloomberg) -- Yemen’s Houthis vowed they would keep attacking ships in the Red Sea, even after the US launched a fourth round of missiles strikes against them.

“It is an honor for our people to be in such a confrontation with these evil forces,” Abdul Malik al-Houthi, the head of the Iran-backed militant group, said in a televised speech on Thursday, citing the US, the UK and Israel. The Houthis are now in “direct confrontation” with all three and are taking steps to bolster their military capabilities, he said.

The Houthis have ramped up attacks on vessels in and around the southern Red Sea since mid-November, roiling shipping markets and sending freight costs higher. The group says its campaign is to support Hamas in its war against Israel in Gaza.

Read more: Who Are the Houthis Being Hit With US, UK Airstrikes?: QuickTake

The Houthis have ignored repeated warnings form the West to stop. On Jan. 12, the US and UK launched the first of their strikes against them, targeting military airports, radar installations and storage and launch sites for drones and missiles.

US officials have said that while they don’t expect to deter the Houthis, they believe they are degrading the group’s ability to fire missiles and drones at ships. Still, this week the Houthis have hit three more merchant vessels, including a US-owned commodities carrier on Wednesday evening. 

Al-Houthi’s remarks raise the prospect of a prolonged conflict in the region as the fallout from Israel’s war against Hamas worsens.

“Our maritime operations are having a very big impact and that’s what we want,” he said. 

Read more: Red Sea Shipping Chaos Worsens as US Strikes Broaden Crisis

Many shipping companies and energy firms are avoiding the Red Sea, which normally handles 12% of global seaborne trade. Plenty of vessels are instead taking the much longer journey to and from Europe by going around southern Africa.

Since the war between Israel and Hamas erupted in October, US bases have come under fire from Iran-backed groups in Iraq and Syria, and Tehran has struck targets in neighboring countries. Hezbollah, one of the most powerful militias in the Middle East, has also engaged in cross-border fire with Israel.

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Al-Houthi, whose group receives significant financial, military and intelligence support from Tehran and is eager to elevate its standing within Iran’s alliance of regional proxies, said the group wanted to be a “real pressure point” on the US and Israel.

The Palestinian cause is “one that we live by and die by,” he added.

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