Damascus - The Islamic State group consolidated its control of the Iraq-Syria border Friday after capturing an Iraqi provincial capital and a famed Syrian heritage site in an offensive that has sparked criticism of US military strategy in the region.
A suicide bomber from the extremist Sunni organisation also attacked a Shia mosque in Saudi Arabia, raising sectarian tensions.
The jihadists, who now control roughly half of Syria, reinforced their self-declared transfrontier "caliphate" by seizing Syria's Al-Tanaf crossing on the Damascus-Baghdad highway late Thursday.
It was the last regime-held border crossing with Iraq.
The jihadist surge, which has also seen it take Ramadi, capital of Anbar province, and the ancient Syrian city of Palmyra in the past week, comes despite eight months of US-led air strikes.
It has sparked an exodus of tens of thousands of civilians in both countries and raised fears IS will repeat at Palmyra the destruction it has already wreaked at ancient sites in Iraq's Nimrud and Mosul.
AFP