It was not clear whether the 70,426-tonne Formosaproduct Cosmos, owned by the island's Formosa Plastics Marine Corp, had directly asked the mainland for an armed escort. Taiwanese media did not report the mission yesterday.

The Taiwanese government said last week that it had no plan to ask the PLA for naval escorts off the Somali coast. All Taiwanese cargo and fishing vessels should seek help from 'the nearest warships' if attacked by pirates in the trouble areas, it said.

Yesterday's mission is historic for the PLA, whose primary political objective is to capture Taiwan if the island moves to seek full independence. It also serves as a political message for Beijing, which sees itself as the sole legitimate protector of all Chinese.

The mainland's Taiwan Affairs Office earlier said Taiwanese vessels could ask for armed escorts from the PLA Navy through the mainland's Association for Relations Across the Taiwan Strait, and the island's semi-official Straits Exchange Foundation.

Formosa Plastics Marine is a subsidiary of the Formosa Plastics Group, the island's biggest private company, which is run by the family of the late pro-mainland tycoon, Wang Yung-ching.

Xinhua said the convoy's mission covered 553 nautical miles, starting from east of the Mandab Strait - the key passage connecting the Red Sea and the Gulf of Aden.

Beijing sent two missile-armed destroyers and a large supply vessel to Africa last month to protect Chinese ships, including vessels from Hong Kong, Macau and Taiwan, against pirates.

In the convoy's first mission, it escorted four Chinese merchant vessels, including one from Hong Kong.