A car bomb in south-west Pakistan has killed three Chinese engineers and injured 10 other people, police and officials say.
Some of the wounded were airlifted to Karachi for treatment
The blast occurred as the engineers were being taken to work on a project developing port facilities in the city of Gwadar, near the border with Iran.
Police said the attack appeared to be a remote-control detonation.
It is the first major attack on foreign workers since a suicide bomber killed 11 French engineers in Karachi in 2002.
'Aim to terrorise'
Police said the latest attack could be the work of Islamic extremists or local nationalists opposed to the port project.
Deputy superintendent Lal Jan said: "This is clearly terrorism. The aim was to terrorise Chinese working at the port."
The Chinese government demanded an investigation into the attack and told its diplomatic missions to help the victims.
Pakistani President Pervez Musharraf said a full probe had been ordered and the perpetrators would be punished.
"The government and people of Pakistan strongly condemn this barbaric act of terrorism and will never allow a few terrorists to undermine Pakistan-China friendship and co-operation," he wrote to Chinese President Hu Jintao.
The blast occurred at around 9am (0400 GMT) on Monday as 12 Chinese engineers were being taken to work in a van.
"A car was parked near the port and it exploded as the bus reached the port," Sattar Lasi, Gwadar's police chief, told the Associated Press news agency.
Doctors confirmed three Chinese were dead and six others were seriously hurt. Four of the injured were airlifted to Karachi.
Two Pakistanis, a driver and a security guard, were among the wounded.
Authorities have not ruled out a suicide attack. No human remains were found in the car but the force of the blast had almost destroyed it.
Ghafoor Baluch, a fisherman who lives nearby, told AP the explosion shook his home.
"We saw pieces of metal from the car strewn on the beach and stuck in nearby trees."
The motive for the attack remains unclear.
The Sheraton blast in Karachi in 2002 killed 11 Frenchmen
Islamic militants have targeted foreigners in the past, but not in this area.
Some local nationalist groups have expressed opposition to the port, saying the benefits would bypass Baluchistan province and go to neighbouring Punjab.
More than 400 Chinese engineers and construction workers are working on the $250m project.
Sun Xiyo, general manager of the company in Gwadar, said: "We will continue our work at Gwadar."
China is a key trading partner and ally of Pakistan and is funding 80% of the port project, which will be completed next year.
This is the first time Chinese workers have been targeted in Pakistan.
The most deadly attack on foreign workers in the recent past occurred outside Karachi's Sheraton hotel in May 2002 when a suicide bomber killed 11 French naval engineers helping Pakistan's navy develop a new submarine.
A month later, a suicide bomb attack outside the US consulate in Karachi left 14 people, all Pakistanis, dead.