A car bomb has killed two security officers and injured four others in southern Turkey.

The bomb went off as the soldiers were travelling on a road in the Diyarbakir province.

The attack came after the Kurdistan Workers Party PKK rebel group threatened to no longer observe a truce, following Turkish air strikes on its positions in northern Iraq.

Meanwhile, the White House has said it welcomed Turkey's increased focus and efforts to fight Islamic State, and called the Kurdish militant PKK in Turkey a "terrorist" organisation.