A powerful magnitude-7.7 earthquake struck in the sea south of Cuba on Tuesday, triggering a tsunami warning for Cuba, Jamaica and the Cayman Islands, the United States Geological Survey (USGS) and the International Tsunami Information Center said.

The epicentre of the earthquake, initially reported as magnitude 7.3 before being upgraded, was between Jamaica, the Cayman Islands and Cuba, at a shallow depth of 6.2 miles (10 km).

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The quake was not strongly felt in the Cuban capital of Havana or Kingston, Jamaica, according to Reuters News Agency witnesses.

Meanwhile, Mikhail Campbell, a police media relations officer in the Cayman Islands, said he was not immediately aware of any reports of serious damage.

Tsunami warnings were quickly issued.

"Hazardous tsunami waves from this earthquake are possible within 300 km (186 miles) of the epicentre along the coasts of Jamaica ... Cayman Islands and Cuba," the International Tsunami Information Center said.

The disaster management agency for the Cayman Islands government on Twitter urged people to move away from coastal areas and said those in low-lying areas should "evacuate vertically" in strong multistorey buildings.