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has started rolling , local media reported on Sunday, which officials blamed on heat, impacting hydropower generation, and surging electricity demand blamed in part on mining.

Power cuts in the peak summer months are not uncommon in Iran, but a report this month said precipitation was down 43 percent compared to the country's long-term average, warning of reduced water supplies for the year.

and several other cities have been hit by unannounced power that sparked complaints from consumers, disrupted businesses and damaged household appliances, Iran's state television reported.

Rolling blackouts for the capital, Alborz and Khorasan Razavi provinces were announced by provincial power distribution companies, with neighbourhoods losing power for at least two hours until evening.

Tehran had experienced brief unplanned outages on Saturday, said AFP correspondents after power cuts had also hit other major cities such as Shiraz and Isfahan from Friday, according to IRNA and ISNA news agencies.

The national grid is overburdened from drought as well as "rising temperature and consumption and a new phenomenon called crypto-currencies," ISNA quoted national electricity company director Mohammad Hassan Motevalizadeh as saying.

Iranian officials have regularly blamed "illegal" crypto miners for using vast amounts of electricity through the so-called blockchain process used to generate valuable digital assets like bitcoin.

Electricity company spokesman Mostafa Rajabi Mashhadi said Saturday the company cut power to four "overusing" government bodies, while registered crypto mining farms had voluntarily shut down operations to ease the burden.

Tehran's blackout on Saturday also impacted two chess players competing in an Asian championship held online when the chess federation building lost power with no backup.

"Two of Iran's best lost (due to) a sudden power cut," IRNA quoted federation chief Mohsen Samizadeh as saying.

The competition's organiser on the Iranian side, Shadi Paridar, told ISNA that the players "returned to their hotel with tears in their eyes".

State TV said matches continued on Sunday with backup generators.