Gunmen burst into a compound in northern Afghanistan early on Thursday, killing 11 Chinese road workers and wounding five, an official from the Chinese Embassy in Kabul said. This is the bloodiest attack on foreigners since the Taliban fell.
The raid occurred 35 km (22 miles) south of the city of Kunduz, until now deemed a secure area as Islamic insurgents concentrate their attacks in Afghanistan's south and east.
It came just two days after about 100 Chinese workers had arrived at the site.
"Ten people died on the spot and several (others) were wounded, one of whom has since died," said an official from the Chinese Embassy in Kabul who declined to be identified. The attack took place at around (2030 GMT on Wednesday).
"They were working on a road paving project for a Chinese company. The project is being financed by the World Bank."
Security guards exchanged fire with about 20 assailants.
The attack will deal a body blow to Afghanistan's efforts to rebuild a country shattered by decades of war and occupation.
President Hamid Karzai, installed in power after US forces helped topple the Taliban in late 2001, is on a visit to the United States.
Remnants of the ousted militia and their militant allies including al-Qaeda have vowed to attack foreign and Afghan troops as well as aid organizations, and disrupt elections due in September.
The rebels have been most active in their old strongholds in the south and east, but an attack in the northwest last week that killed three foreigners and two Afghans from the Medecins Sans Frontieres aid group, and the Kunduz raid, have raised concern that the insurgency is spreading.
Ambassador to visit
The reason for the attack just outside the provincial capital of Kunduz was not known. China has pledged to help Afghanistan rebuild a major irrigation project near Kabul.
The Chinese Foreign Ministry had no immediate comment. The embassy official said the ambassador to Afghanistan, Sun Yuxi, would fly to the area on Thursday.
Kunduz is 250 km (156 miles) north of Kabul and takes up to seven hours to reach by road.
The official said the wounded would be taken to a German hospital in Kunduz, where a provincial-civilian team led by German troops has been operating.
No decision has been taken on whether to pull other Chinese workers out of the area.
"The first thing is to take care of the wounded," the embassy official said.
Kunduz was the scene of one of the fiercest clashes in the US-led war on the Taliban in late 2001. Hundreds of militants were killed there and many were captured and imprisoned.
Militant attacks on Chinese overseas are rare.
A car bomb exploded at one of Pakistan's biggest construction projects in May, killing three Chinese technicians and wounding 11 people in what Pakistani President Pervez Musharraf called a barbaric act of terrorism.
In April, seven Chinese construction workers were briefly taken hostage in the volatile Iraqi town of Falluja and released 36 hours later.
As part of warming bilateral ties, China has agreed to write off debts owed by Afghanistan.