<span style="color: #222222;">Venezuelans are voting in a referendum on Sunday which has ratcheted up the tension between the South American country and its neighbour, Guyana. The Venezuelan government has called the referendum to measure popular support for its historical claim to a contested oil-rich swathe of jungle currently administered by Guyana.</span><br />'' <span style="color: #222222;"> </span><br />'' <span style="color: #222222;">The 159,500-sq-km region is known as Essequibo and makes up two-thirds of the total of the land currently controlled by Guyana. It is home to 125,000 of Guyana's 800,000 citizens. The dispute over the area has been rumbling on for more than a century. In 1966, Britain and Venezuela reached an agreement – known as the Geneva Agreement – to establish a commission made up of representatives of Guyana, which became independent from Britain that same year, and Venezuela to revisit the territorial dispute.</span><br />