Three Chinese engineers have been killed by gunmen in Pakistan's troubled south-western province of Balochistan, police have said.
Their Pakistani driver also died in the attack in the town of Hab, near Karachi. The engineers had worked at a local cement plant, police said.
Unconfirmed reports say the Baloch Liberation Army claimed the attack.
Chinese workers have been targeted in recent years by local militants involved in a long-running insurgency.
Pakistan's government condemned the killings as an "act of terrorism" aimed at harming ties with China and promised all measures to prevent such acts in future.
'Act of terrorism'
The engineers and their drivers were ambushed in their vehicle by gunmen on motorcycles, police said.
The attackers struck as the workers were leaving the Attock cement factory.
Two Chinese died on the spot while the third succumbed to his injuries at a hospital in Karachi, police said.
They said engineers were not accompanied by their guards at the time of the attack.
A local police chief condemned the incident as "an open act of terrorism".
"Terrorists have killed innocent Chinese who have come to work here to help Pakistan," Pervez Zahoor was quoted as saying by the Associated Press news agency.
In recent years, Chinese workers have been the target of militant attacks in Balochistan, where an insurgency involving armed tribal nationalists has been going on for some time, the BBC's Zaffar Abbas in Islamabad says.
A large number of Chinese construction engineers and technicians have been working on various state-run projects across Pakistan.
In Balochistan, they have been mostly involved in the construction of a big port at Gwadar.
Pakistan has very close relations with China as Beijing has been its major supporter in defence and other projects, our correspondent says.
The latest incident comes as President Pervez Musharraf is scheduled to make an official visit to Beijing over the weekend.
In May 2004, three Chinese port workers were killed in a similar attack at Gwadar.