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Both Venezuela and Guyana lay claim to the Essequibo region

By Rachelle Krygier & Vanessa Buschschlüter

BBC Monitoring & BBC News

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.

The 159,500-sq-km (61,600-square-mile) 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 1899, an international arbitral tribunal awarded the area to Britain, which at the time was the colonial power ruling over Guyana, or British Guiana, as it was then known.

Guyana: Key facts

Capital: Georgetown