Pakistan’s army said on Saturday that attackers from Iran killed four of its border patrol soldiers.

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

The incident took place in the Kech district in southwestern Baluchistan province, which shares a long lawless border with Afghanistan and Iran.

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

No one has claimed responsibility.

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