JERUSALEM (AP) -- A European naval force detained six suspected pirates on Friday after they opened fire on an oil tanker traveling through the Gulf of Aden, officials said, likely part of a growing number of piracy attacks emanating from Somalia.

The attack on the Marshall Islands-flagged Chrystal Arctic comes as Yemen's Houthi rebels have also been attacking ships traveling through the crucial waterway, the Red Sea and the Bab el-Mandeb Strait connecting them. The assaults have slowed commercial traffic through the key maritime route onward to the Suez Canal and the Mediterranean Sea.

The pirates shot at the tanker from a small ship "carrying weapons and ladders," according to the British military's United Kingdom Maritime Trade Operations center, which oversees Mideast shipping routes. The pirates opened fire first at the Chrystal Arctic, whose armed, onboard security team returned fire at them, the UKMTO said.

The pirates then abandoned their attempt to take the tanker, which continued on its way with all its crew safe, the UKMTO said.

Hours later, the European Union naval force in the region known as Operation Atalanta said a frigate operating in the region detained six suspected pirates. The frigate seized the pirates given "the unsafe condition of their skiff" and said that some had "injuries of varied severity."

It wasn't immediately clear if those injured suffered gunshot wounds from the exchange of fire with the Chrystal Arctic. The EU force declined to elaborate "due to the security of the operations."

Once-rampant piracy off the Somali coast diminished after a peak in 2011. That year, there were 237 reported attacks in waters off Somalia. Somali piracy in the region at the time cost the world's economy some $7 billion -- with $160 million paid out in ransoms, according to the Oceans Beyond Piracy monitoring group.

Increased naval patrols, a strengthening central government in Mogadishu, Somalia's capital, and other efforts saw the piracy beaten back.

However, concerns about new attacks have grown in recent months. In the first quarter of 2024, there have been five reported incidents off Somalia, according to the International Maritime Bureau.

"These incidents were attributed to Somali pirates who demonstrate mounting capabilities, targeting vessels at great distances, from the Somali coast," the bureau warned in April. It added that there had been "several reported hijacked dhows and fishing vessels, which are ideal mother ships to launch attacks at distances from the Somali coastline."

In March, the Indian navy detained dozens of pirates who seized a bulk carrier and took its 17 crew hostage. In April, pirates releases 23 crew members of the Bangladesh-flagged cargo carrier MV Abdullah after seizing the vessel. The terms of the release aren't immediately known.

These attacks come as the Houthi campaign targeting shipping since November as part of their pressure campaign to stop the Israel-Hamas war raging in the Gaza Strip.