ISLAMABAD (Reuters) -Pakistan's military said on Tuesday that a suicide bomb attack that killed five Chinese engineers in March was planned in neighbouring Afghanistan, and that the bomber was also an Afghan national.

The suicide bomber rammed a vehicle into a convoy of Chinese engineers working on a dam project in northwest Pakistan, killing six people.

"The entire attack was planned in Afghanistan, the car used in it was also prepared in Afghanistan, and the suicide bomber was also an Afghan national," Pakistan military spokesman Major-General Ahmed Sharif told a news conference in Islamabad.

Afghanistan's Taliban-run administration did not immediately respond to a request for comment.

Kabul has previously said rising violence in Pakistan is a domestic issue for Islamabad and denied allowing the use of its territory by militants.

The Taliban are also seeking economic ties with China, the first country to formally appoint an ambassador to Kabul under the Taliban, and have said they would like to join Xi Jinping's Belt and Road and the China-Pakistan Economic Corridor (CPEC).

China has stressed to the Taliban the importance of security in the region according to experts and statements from Beijing, including a public agreement in May 2023 by all three countries during a meeting in Islamabad to strengthen counter-terrorism cooperation.

Sharif said four main suspects of the plot to target the Chinese engineers have been arrested.

He added that security for 29,000 Chinese nationals in Pakistan, of which 2,500 were working on CPEC projects and 5,500 on other development projects, was the top priority for security institutions.

Relations between Pakistan and Afghanistan have soured in recent months with Islamabad saying the Taliban-run administration in Kabul is not doing enough to tackle militant groups targeting Pakistan.

Islamabad has gone as far as to say some elements in the Taliban are facilitating the Islamist militants of Tehreek-e-Taliban Pakistan (TTP) - which is not affiliated with the Taliban, but has long pledged loyalty to the Afghanistan-based movement.

"TTP militants are using Afghanistan's territory to destabalise the security situation in Pakistan," Sharif said, adding that TTP militants were also procuring advanced weaponry from Afghanistan to carry out the attacks.

He warned that the Pakistan military will go to "any extent" to tackle militants and their facilitators.

In March, Pakistan said it targeted militant hideouts inside Afghanistan, which Taliban officials claimed were air strikes. Taliban run-security forces responded with heavy weapons fire at Pakistani security posts on the border.

(Reporting by Asif Shahzad in Islamabad; Writing by Gibran Peshimam; Editing by YP Rajesh and Chizu Nomiyama)

By Asif Shahzad