NAIROBI, Kenya — The U.S. Navy on Monday helped free the fifth ship in a week hijacked by Somalia pirates, attempting to bring security to crucial shipping routes between the Red Sea and Indian Ocean.

Pirates released the Taiwanese fishing vessel 5 1/2 months after seizing it. U.S. naval personnel have been telling the pirates by radio to abandon hijacked vessels, get back in their small skiffs and return to Somalia.

“We encourage pirates to leave the ships,” said Cmdr. Lydia Robertson of the U.S. Fifth Fleet in Bahrain. “We tell them, you get in the skiff, you leave, you do not take any hostages.”

Robertson said the Navy was in contact with two remaining ships held by pirates in Somali waters.

The latest fishing vessel freed by the U.S. Navy had two Taiwanese and 12 Chinese crew members aboard when it was hijacked 137 miles off the coast of Somalia’s capital, Mogadishu, in May.

Pirates killed one of the crew members in June, according to Andrew Mwangura, head of Seafarers Assistance Program’s Kenyan chapter. The International Maritime Bureau said it had heard reports of a shooting but had no official confirmation of the death.

Two other boats hijacked by Somali pirates in May were freed after U.S. Navy personnel spoke to them by radio.

U.S. sailors also boarded a North Korean ship to treat crew members who overpowered their hijackers, and a U.S. naval vessel fired on pirate skiffs tied to a Japanese-owned ship.

Somalia’s lawless coastlines are a haven for heavily armed pirates who use speedboats with Global Positioning System equipment, anti-tank rocket launchers and grenades. The country has lacked a functioning government since 1991, when rival warlords overthrew dictator Mohamed Siad Barre and turned on each other.