A suicide bomber rammed a vehicle into a convoy of Chinese engineers working on a dam project in northwest Pakistan on Tuesday, killing six people, police said, the third major attack on Chinese interests in the South Asian country in a week.

The first two attacks hit an airbase and a port in the southwest province of Balochistan where China is heavily investing in infrastructure projects.

The engineers were on their way from Islamabad to their camp at the dam construction site in Dasu in the Khyber Pakhtunkhwa province, Mohammad Ali Gandapur, the regional police chief, said.

"Five Chinese nationals and their Pakistani driver were killed in the attack," Gandapur said.

Dasu is the site of a major dam and the area has been attacked in the past. A blast on a bus killed 13 people, including nine Chinese nationals, in 2021.

Chinese engineers have been working on a number of projects in Pakistan, with Beijing investing over US$65 billion in infrastructure projects as part of the China Pakistan Economic Corridor under the Belt and Road initiative.

Pakistan's Interior Minister Mohsin Naqvi was pictured arriving at China's embassy in Islamabad within hours of the bombing.

"The enemy aimed its attack at the citizens of Pakistan's most trusted friend country," he said in a statement. "A robust response will be delivered to the perpetrators."

No one claimed responsibility for Tuesday's attack, nor was there a claim for the 2021 attack.

The attacks come a week before Prime Minister Shehbaz Sharif is expected to fly to Beijing, according to a source in the Prime Minister's Office. It will be Sharif's first visit since taking office following February elections.

Pakistani Foreign Minister Ishaq Dar condemned the attack, and said the country would continue to fight back against militants. (Reuters/AFP)