The Iranian navy has freed 28 Chinese crew members less than a day after their cargo ship was hijacked by Somali pirates off the Islamic republic's south coast, Chinese state media said Saturday.

The pirates attacked the ship early Friday in the Gulf of Oman near the Iranian port of Chabahar, clambering onto the vessel with ladders and opening fire, said the official Xinhua news agency, citing China's embassy in Tehran.

It was the latest episode of Chinese getting into trouble as the country's firms do more business abroad -- Chinese workers were kidnapped in Sudan and Egypt earlier this year, and Chinese sailors have been held captive before.

Following the hijacking Friday, China's ambassador in Tehran, Yu Hongyang, demanded swift action from Iran, which dispatched its navy to rescue the crew.

Two warships caught up late Friday with the ship, the Panama-registered Xianghuamen which belongs to a company in eastern China, and the pirates "threw their weapons into the sea and surrendered to the Iranian navy," Xinhua said.

The ambassador had earlier urged Tehran to make the safety of the crew its "first priority", adding that the Chinese government and foreign ministry had expressed concern about the incident.

The freighter, which had set off from Singapore and was heading to a port in southwestern Iran, had its engine damaged in the attack and was being repaired, Xinhua said. It will continue to an Iranian port after repairs.