The temblor occurred yesterday just before 4 pm about 106 miles (172 kilometers) east of Havana, according to the US Geological Survey. The closest city to the epicentre was Corralillo, 17 miles (28 kilometers) to the southwest.
In Old Havana, the quake was felt clearly by workers in two 6-floor buildings that were temporarily evacuated. It appeared to last around 30 seconds.
Sandor Polo, a 31-year-old waiter, said he was delivering food to a third-floor office when boxes suddenly began to move and workers started yelling.
"Everything was moving," said Nuria Oquendo, a 44-year-old office assistant who was on the sixth floor of a neighbouring building when it began to move back and forth. "You could really feel it, very clear, very defined."
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Like Polo, she had never been in an earthquake before. She called the experience unsettling, but said she wasn't scared. "Not frightened, but a sensation that something strange is going on," Oquendo said.
The USGS initially reported a magnitude of 5.0, and later upgraded it to 5.1. The quake struck at a depth of six miles (10 kilometers).
Cuba is not as known for seismic activity as other parts of Latin America, especially countries along the Pacific Rim of Fire.
But a number of significant quakes have hit the island over the years, including one in 1932 that killed eight people and damaged 80 percent of the buildings in the eastern city of Santiago, according to US National Geophysical Data Centre records.