Somali pirates responsible for hijacking a Chinese cargo ship in the Indian Ocean threatened Tuesday to kill its 25 crew members if a rescue operation was attempted.

"We tell China not to endanger the lives of their people with any rescue operation," Hassan, a member of the gang that seized the vessel on Monday, told Reuters by phone.

"If they try that we will execute the whole crew ... we tell them to change their mind regarding any rescue, otherwise they will regret it. We know what they are planning to do."

A government spokesman said China is making an "all-out" effort to rescue the cargo ship.

The De Xin Hai and its 25 crew members were seized by pirates in the Indian Ocean about 700 miles east of the lawless Somali coastline.

Foreign Ministry spokesman Ma Zhaoxu said China has launched a "contingency mechanism" in the wake of the hijacking and ordered missions abroad to verify developments and notify relevant countries.

It has also issued warnings to Chinese ships to stay away from the area "in case of accident or danger."

"We will continue to follow closely the developments and make all-out efforts to rescue the hijacked ship and personnel," he said, without elaborating on details.

It is the first successful attack on a Chinese vessel since the country deployed three naval warships to the region last year. A previous attack on a Chinese vessel last year was repelled when the crew used homemade Molotov cocktails to fight off their attackers.

A spokesman with Qingdao Ocean Shipping Co., Ltd., which owns the vessel, said the company is working on comforting the families of those kidnapped. He declined to give his name because he was not authorized to speak with media. He said the company was working with the Transport Ministry and other relevant ministries.

China's anti-piracy mission was the first international combat mission for China's navy outside of its home waters. Countries as diverse as Britain, India, Iran, the U.S., France and Germany have naval forces in the waters or on their way there.

Spurred by poverty in Somalia, pirates have made an estimated $30 million hijacking ships for ransom last year, seizing more than 40 vessels off the African nation's 1,880-mile coastline.

Somali pirates have recently ramped up attacks after a period of quiet during poor weather. They use sophisticated equipment and so-called larger "mother ships" to enable them to strike hundreds of miles offshore. The multimillion-dollar ransoms they share are a fortune in their impoverished and war-ravaged country.

A total of 146 people, including the crew of the De Xin Hai, are currently being held hostage by pirates.

The Associated Press contributed to this report.