A massive blackout struck three Central Asian countries Tuesday as a result of an undisclosed catastrophe, leaving millions of people without power.

At around midday local time, the capitals of Kyrgyzstan and Uzbekistan, as well as Kazakhstan's industrial hub Almaty, lost power, with media and officials saying that the blackouts had spread well into the three countries' provinces.

The power outage was caused by an accident in Kazakhstan's electrical grid, according to Uzbekistan's energy ministry, which issued a message on its official Telegram channel.

"As a result of a major accident in the power grids of the Republic of Kazakhstan, there was a power outage in the cities of Almaty, Shymkent, Taras, Turkestan (regions) and adjacent areas," the statement added.

"The Uzbek power grid, which is connected to the Unified Power Grid, was damaged as a result of an accident that led to sudden changes in voltage and frequency on 530 lines from Kazakhstan," it concluded.

Power was off "due to an accident in the regional electricity grid," a representative for Kyrgyzstan's energy ministry told AFP via phone.