AMMAN: Syrian troops massed on the Turkish border overnight, witnesses said on Thursday, escalating tensions with Ankara as President Bashar al-Assad uses increasing military force to try to crush a popular revolt.Refugees from the northwestern province of Idlib said armoured vehicles and troops were now as close as 500 metres from the border in the Khirbat al-Joz area. A Reuters photographer in the Turkish border village of Guvecci saw three uniformed Syrian soldiers with a machinegun positioned on the roof of a house on top of a hill. (Reuters)