ISLAMABAD -- Pakistani Prime Minister Shehbaz Sharif on Tuesday vowed to promptly bring to justice the perpetrators and accomplices of the attack on Chinese nationals in the country's northwest Khyber Pakhtunkhwa (KP) province when visiting the Chinese Embassy in Pakistan, the Prime Minister's office said.

Five Chinese nationals and one Pakistani were killed when a vehicle from the Dasu Hydropower Project, being constructed by a Chinese company in the province, was attacked by terrorists on Tuesday afternoon, the Chinese Embassy in Pakistan confirmed in a statement.

In a meeting with Chinese Ambassador to Pakistan Jiang Zaidong during his visit, Sharif offered deep and sincere condolence to the families of the Chinese victims, describing the terrorist attack as "horrific."

Pakistan will make every effort to work with China to properly deal with the aftermath of the incident, conduct the investigation promptly and thoroughly, and bring the perpetrators to justice, the prime minister said, adding that further measures will be taken to comprehensively strengthen the security of Chinese personnel, projects, and institutions in Pakistan.

"We will not let the despicable efforts to harm Pakistan-China friendship succeed," he added.

Jiang said that China strongly condemns this terrorist act, expresses deep condolences to the victims of both countries and is making full efforts to deal with the aftermath of the incident.

"We urge the Pakistani side to speed up the investigation, promptly bring the perpetrators to justice, earnestly and effectively protect the safety of Chinese citizens in Pakistan and ensure that similar incidents will not happen again," said the Chinese ambassador.

The incident happened in the Shangla area of the province, where the attacker rammed an explosive-laden vehicle into a convoy escorted by five vehicles of security forces, sources from KP's police told Xinhua.

One of the vehicles of the 13-vehicle convoy caught fire and fell into a ravine, following the attack, the sources added.

The area was cordoned off for investigations and the injured were shifted to hospital.

No group has claimed the attack yet.

The incident has also been condemned by Pakistan's President Asif Ali Zardari, and Pakistan's foreign ministry and army. They expressed their condolences to the bereaved families, and vowed that the country will never let enemies of Pakistan-China friendship succeed in their mission.