The image “” cannot be displayed, because it contains errors.NAIROBI, Kenya (AP) — Somali pirates gave up control of two ships hijacked months earlier and U.S. Navy escorted the boats to safer waters Sunday as it stepped up efforts to bring security to the seas off the chaotic Horn of Africa nation.

The pirates climbed into small skiffs and headed back to Somalia after speaking by radio to U.S. naval personnel. A Navy ship and helicopter guided the South Korean-owned boats Mavuno 1 and 2 further out to sea.

It was the third time in a week the U.S. has intervened to help ships hijacked by Somali pirates. Sailors boarded a North Korean ship to give medical assistance to crew members who overpowered their hijackers, and a U.S. naval vessel fired on pirate skiffs tied to a Japanese-owned ship.

Naval personnel boarded the South Korean-owned ships and gave medical checkups to the crew, said Cmdr. Lydia Robertson of the U.S. Fifth Fleet in Bahrain. No injuries were reported. The two Tanzanian-flagged boats were seized May 15.

The Navy was also urging pirates to leave the Japanese ship and two hijacked boats in the region and sail back to Somalia, she told The Associated Press.

“We’re very happy with this development and hope it happens with the other ships off the coast,” Robertson said. She gave no indication of the content of the conversations.

Robertson said the increase in U.S. military interventions was mostly due to the a surge in piracy. As the Navy moved ships into the area to respond to one incident, increased contact with other hijacked ships in the area was more likely, she said.

“It’s not that it’s a change in focus,” Robertson said. “But we had the opportunity to put some pressure on the pirates and say it’s time to leave, we need to free these ships.”

South Korea said all 24 sailors on board the two ships freed Sunday were safe. The Foreign Ministry said the ships were being escorted to Aden port in Yemen at the request of the South Korean government. The two dozen sailors included 10 Chinese, four South Koreans, three Vietnamese, three Indians and four Indonesians.

“The government strongly condemns the international pirate activities that resulted in innocent sailors seized in high seas and held in captivity for a long time,” the ministry said.

South Korea said it appreciated the U.S. and Somalian help in freeing the men.

South Korean media have reported that the Somali pirates were demanding between $700,000 and $1 million in ransom. Robertson made no comment on ransom demands, deferring to the shipping company.

Last year, another South Korean fishing vessel was captured off Somalia and released three months later after a ransom of more than $800,000 was paid.

Somalia lies close to crucial shipping routes connecting the Red Sea with the Indian Ocean.

The country has had no effective government since 1991, when warlords ousted a dictatorship and then turned on each other, making it difficult to prevent attacks along Somalia’s 1,880-mile coastline.

Last year, another South Korean fishing vessel was captured off Somalia and released three months later after a ransom of more than $800,000 was paid.

Associated Press writer Hyung-jin Kim in Seoul contributed to this report