HAVANA (AFP) - Cuba declared three days of national mourning after the death on Tuesday of Venezuelan President Hugo Chavez, the Communist nation's closest regional ally and main economic support.

In an official statement read out on state television, the Cuban government said Mr Chavez had "stood by Fidel (Castro) like a true son," during Mr Chavez's 14 years in power.

Cuba's revolutionary icon, now 86, stepped aside as president in 2006 during a health crisis of his own.

"The Cuban people think of him as one of their greatest sons, and have admired, followed and loved him as one of their own. Chavez is Cuban too! He felt in his flesh and bones our hard times and problems, and he did everything that he could, with extraordinary generosity," said a communique from the Council of State led by President Raul Castro.

Mr Chavez's death is deeply alarming news for Havana, regardless of the fact it was not entirely unexpected after Mr Chavez's long cancer fight.

Cuba's main governing challenge is trying to stay afloat economically in order to project its one-party regime into the future, without making too many sacrifices to market economics.

And with Mr Chavez's death, it has lost the economic security it has known for more than a decade. The Chavez boost allowed Havana to muddle through grinding hardship without sinking into full-on economic crisis, and without having to adopt major market-minded economic reforms.

Aside from being Venezuela's closest regional ally, Cuba relies on cut-rate Venezuelan oil to fuel its crippled economy, run power plants and get food into cities and tourist areas.

And officially Cuba's leading export is not sugar or nickel but the US$6 billion (S$7.5 billion) a year Havana gets from Caracas in exchange for the services of more than 40,000 Cuban doctors and health care workers.