HAVANA, March 21 - Cuba's national electric grid collapsed on Saturday for the second time in a week amid the U.S.-imposed oil blockade, officials announced, as the communist government struggles to keep the lights on for its 10 million people with decrepit infrastructure.

"At 18:32 (2232 GMT), a total disconnection of the National Electric Power System occurred. We will continue to provide updates," the state utility Union Electrica said on social media.