In poor communities around Venezuela, residents are increasingly relying on the services of Cuban doctors and other professionals. In exchange, Cuba gets an estimated $3.2 billion in Venezuelan oil. Increasingly, the doctors are a flashpoint for the unrest that has rocked the country since February and is blamed for around 40 deaths.

The mostly middle- and upper-class anti-government protesters see the doctors-for-oil deal as an intolerable giveaway of Venezuela's vast petroleum wealth, as the country suffers from high inflation, shortages of basic goods and one of the world's highest homicide rates. Venezuela sends about 100,000 barrels of oil every day to Cuba, which accounts for half the island's domestic energy consumption.

In February, dozens of people carrying signs saying "Cuba go home" physically harassed a Cuban baseball team playing in a tournament on Margarita Island. More recently, assailants burned down a medical clinic staffed by Cubans in the western city of Barquisimeto.

For supporters of Maduro's government, especially residents in low-income communities, the doctors are an example of concrete improvements delivered under the late President Hugo Chavez and now Maduro. There's no sign that the doctors will decamp anytime soon, and Maduro has vowed the anti-Cuba sentiment will only "bolster our conviction that we must strengthen our brotherhood."

--Reporting by the Associated Press