"Our primary target is not striking them but dispelling them.

"If the pirates make direct threats against the warships or the vessels we escort, the fleet will take counter measures."

A surge in attacks this year in the Gulf of Aden and Indian Ocean has pushed up insurance costs, brought the pirates tens of millions of dollars in ransom payments and prompted foreign warships to patrol the area.

While China's growing wealth and influence have seen it involved in peacekeeping operations around the world, it has traditionally kept troops close to home, reflecting a doctrine of non-interference in other nations' affairs.

Possible Japanese deployment

The Chinese deployment comes as Japan also considers sending ships to the area.

Taro Aso, the Japanese prime minister, ordered Yasukazu Hamada, the defence minister, to move ahead with deliberations on how the armed forces could act, the government's senior spokesman told the Reuters news agency.

"He ordered the defence minister to speed up considerations," Takeo Kawamura, the chief cabinet secretary, said.

The dispatch could prove a legal and diplomatic hurdle for Japan, whose military activities overseas are restricted by its pacifist constitution.

Japan's forces have not engaged in combat since the second world war though Japanese forces have been in Iraq to help in reconstruction.