Updated

A car bomb shattered a bus carrying Chinese engineers to a port project in remote southwestern Pakistan (search) on Monday, killing three in what the government called a terrorist attack.

The Chinese government expressed deep concern and urged more protection for some 400 of its citizens working on the port project in Gawadar (search).

The attack occurred as the bus was taking at least 12 Chinese to the port, said Sattar Lasi, the chief of police in Gawadar. The site is about 300 miles west of Karachi, near the border with Iran.

"This is clearly terrorism. The aim was to terrorize the Chinese working at the Gawadar port," said Lal Jan, another senior police official.

Islamic militant groups have targeted foreigners in the past, but never in such a remote part of the country.

Shoaib Suddle, the police chief in Baluchishtan province, said it appeared the bomb was triggered by remote control. Police investigators found fuses and pieces of a cylinder that contained the bomb in the white Suzuki car, said Communications Minister Babar Khan Ghauri.

Only the skeleton of the car remained, and the bus also was heavily damaged, with windows shattered and metal twisted, he said.

Ghafoor Baluch, a fisherman who lives near the scene of the attack, said the explosion shook the walls of his home.

"We saw pieces of metal from the car strewn on the beach and stuck in nearby trees," he said. The explosion left a four-foot crater and smashed the front of the bus, he said.

Hours after the blast, Mohammed Sattar, a police official in Gawadar said they detained two residents for questioning, and that the car, which was used for the attack, had been stolen from Karachi.

Sattar gave no other details, and it was unclear what prompted the police to arrest the men.

The three men killed in the explosion were identified as Hao Ghuangchun, 49; Zhou Xuemeng, 55; and Guo Qihong, whose age was not given. Lasi said 11 others were injured -- nine of them Chinese. The others were a Pakistani driver and security guard.

Prime Minister Zafarullah Khan Jamali condemned the attack and ordered authorities to tighten security.

In Beijing, the Chinese government demanded Pakistan investigate the attack and directed its diplomatic missions in Pakistan to help the victims.

"The Chinese government attaches a high degree of importance to this incident," the Chinese Foreign Ministry said in a statement.

China is an important ally of Pakistan and one of its chief trading partners.

The Chinese all worked for China Harbor Engineering Co., which has been working on the Gawadar project since 2002.

The company asked Pakistani authorities to increase security, but said it had no plans to suspend work.

"We will continue our work at Gawadar port," said Sun Xiyo, general manager of the company in Gawadar. He said more than 400 Chinese engineers and construction workers are involved in the project.

Pakistan has been relatively peaceful in recent months, although a bomb was found and defused outside the U.S. Consulate in Karachi in March.

In December, President Gen. Pervez Musharraf (search) survived two assassination attempts, the last one killing 16 people, most of them passers-by. Musharraf, who was not injured in either attempt, blamed Islamic militants linked to Al Qaeda (search) for the attacks.

In the months after the Sept. 11, 2001, attacks in the United States, Islamic militants outraged by Musharraf's support for Washington carried out a series of deadly attacks on foreigners and minority Pakistani Christians.

On May 8, 2002, a homicide bomber struck a bus carrying French engineers outside the Sheraton Hotel in Karachi, killing 11. The French had been helping the Pakistani armed forces develop a new submarine.