Chinese naval sailors saved a Panamanian ship on Saturday night that had come under attack from pirates in the Gulf of Aden, the second such rescue mission this month, China's Defense Ministry said on Sunday.

The Frigate Hengyang of the People's Liberation Army Navy's 25th convoy fleet received a distress call about 9:30 pm on Saturday, Beijing time. The call said the ALHEERA, an oil tanker, was under attack by five pirates and the ship requested help.

Hengyang set out immediately and dispatched its shipboard helicopter to the area. The helicopter arrived and drove away the suspected pirates around 10:30 pm, the ministry said.

The ship was deemed safe and continued its passage, the ministry said.

Earlier this month, the missile frigate Yulin was dispatched to assist the crew of the Tuvaluan freighter OS35, also in the Gulf of Aden.

On the morning of April 9, the Yulin, from the same convoy, dispatched 16 special forces sailors to board the freighter, where they safely rescued all 19 crew members.

"The rescue operation demonstrated the effectiveness of the Chinese naval forces," Chinese foreign ministry spokeswoman Hua Chunying said at a news briefing the following day.

Chinese naval convoys first began their missions in Gulf of Aden and waters off Somalia on January 2009. Since then, China has sent 26 convoys through, with the latest one leaving April 1. Chinese convoys since have escorted 6,337 ships, including 3,274 ships from other countries and international organizations such as the World Food Programme. They also rescued or aided more than 60 Chinese and foreign ships in the region from local pirates, according to the defense ministry.

Liang Fang, a professor at the PLA's National Defense University, said it is rare for China to disclose details of rescue missions and doing so represents the growing transparency and confidence of the Chinese navy.

"Our convoy's equipment, coordination and emergency response ability have improved throughout the years, transforming the Chinese navy into the most formidable and reliable security force in the region," she said. "By making the details public, people will know they can always count on the Chinese navy for help."

Zhang Junshe, a senior researcher at the PLA Naval Military Studies Research Institute, said the recent rescues and escort missions in general show China is capable and responsible.

"As the strength of the Chinese navy grows, it can shoulder more loads and better safeguard regional and international security," he said.