Brazil announced it had begun deploying troops along its border with Venezuela after the government in Caracas said it intended to annex territory controlled by Guyana, the BBC reported on Thursday.

Agence France-Presse adds that the increased presence is part of efforts to "guarantee the inviolability of the territory".

The oil-rich Essequibo region has been disputed since the 19th century, when Guyana was a British colony. Venezuela renewed its claims after oil and gas deposits were discovered in the sea shelf a few years ago.

A referendum held on Sunday in Venezuela showed that more than 95% of the population supported the accession of Essequibo.

After that, President Nicolás Maduro asked the state oil company to issue mining licenses there and proposed that the National Assembly pass a bill to include the area within Venezuela's borders.

Guyana's troops are on high alert, and Brazil's military said it was moving more troops to the border town of Boa Vista, the capital of Roraima state.

Venezuelan soldiers will have to pass through Brazilian territory if they want to enter Essequibo because of the difficult terrain of the other approaches, writes the BBC.