Havana plunged into darkness as Cuba's power grid collapsed, leaving millions without electricity. Efforts to restore power were hampered by setbacks, impacting vital services. Most Cubans endure prolonged blackouts amid economic strain.

The collapse follows nationwide blackouts last year that plunged Cuba's frail power-generating system into disarray.

Pockets of Cuba's capital Havana saw the lights flicker back on though vast areas of the city and country continued without electricity on Sunday morning, after a nationwide grid collapse that knocked out power to 10 million people.