“A group of terrorists operating from Iranian side attacked a routine border patrol of Pakistani security forces operating along Pakistan-Iran Border,” the army said in a statement.

The firing took place in Kech district in Balochistan province, which shares a long lawless border with Afghanistan and Iran.

A separatist group which has previously been involved in attacks on Pakistani security forces and Chinese interests in the region claimed responsibility in an emailed statement.

The army said Pakistani authorities were making contact with Iran to seek ways of preventing such incidents in future.

Iranian officials were not immediately available to comment on Saturday, an annual holiday in Iran.

Iranian state media said Iran’s embassy in Islamabad “condemned the terrorist attack in Baluchistan state and said terrorism is a common affliction of the two friendly and neighbouring countries.”

Insurgent ethnic nationalist groups in the area say they are fighting for a greater share of regional resources. The Baloch groups operate on both side of the border.

The province is rich in minerals and also has the deep-water Gawadar port, which is being developed with Chinese money as part of Beijing’s $65 billion “Belt and Road” investment in Pakistan.