Caracas  - Polls opened on Sunday morning across Venezuela in a new referendum on the issue of unlimited terms for President Hugo Chavez, amid heavy security measures.

Around 17 million Venezuelans are eligible to vote in the referendum, which will decide on a change to the country's constitution that would see Chavez extend his period in office beyond the currently-mandated two terms, due to end in 2013.

A further term would see Chavez, who has been in power in Venezuela since 1999, in power until at least 2019.

The result of the poll is should be known by the early hours of Monday.

In 2005 Chavez attempted a similar change, but was defeated in the accompanying referendum. dpa