Two Saudi Arabian border guards have been killed and a third injured on the frontier with Iraq in a suicide attack, the Saudi interior ministry has said.

Saudi Arabia’s border with Iraq, which is heavily defended by a series of earthworks and fences and monitored by camera and radar, has been attacked in the past by mortar bombs fired from a distance, but more targeted attacks are rare.

The unidentified attackers opened fire on a border patrol early on Monday near Arar. When security officers responded, one of the attackers was captured and detonated an explosives belt, the ministry said in a brief statement carried by the official Saudi Press Agency.

One of those killed was a senior officer, named by local media as Gen Oudah al-Belawi.

Saudi Arabia stepped up its security on the frontier in July after Islamic State (Isis) militants seized swaths of territory in Iraq, including Anbar province on the kingdom’s border.

Saudi forces have joined US-led air strikes against Isis positions in Syria, and the group has called for “lone-wolf” attacks by sympathisers in the country against its security forces, Shia Muslim minority and foreigners.