A large-scale outage struck the Czech Republic’s electricity grid on July 4, temporarily cutting power to several regions, in what the country’s transmission system operator described as a rare and significant disruption. Neighbouring Slovakia also reported a partial outage.

The temporary power cut hit parts of the Czech capital and in parts of four regions in northern and eastern Czechia. In Prague the subway and trains were brought to a standstill at noon, Prime Minister Petr Fiala said in a post on X.

Prague’s stores and restaurants stayed open, but were only accepting cash payments. The subway service was restored within half an hour, but the power outage persisted longer in other parts of the country. Eight substations in the grid were affected, including a major one in Prague, of which five renewed operations in less than two hours, Czech grid operator ČEPS said

"We are facing an extraordinary and unpleasant situation," Fiala said, as cited by AP.

ČEPS confirmed the disruption in a statement, saying, “There was a large-scale outage in the electricity system today.” The operator added that it was working to determine the precise cause of the failure but has already ruled out a cyberattack.

Industry and Trade Minister Lukas Vlcek said the cause was likely a "mechanical malfunction," AP reported.

The outage forced ČEPS to request emergency assistance under the European Continental Synchronous Area framework, a coordinated mechanism allowing for cross-border support in the event of supply failures.

"Thanks to the cooperation within the Continental Europe Synchronous Area, it was possible to restore the supply relatively quickly," ČEPS said. The company has not yet released details on the number of customers affected or the duration of the blackout in specific areas, Reuters reports.

In neighbouring Slovakia, grid operator SEPS reported that “certain areas” were impacted by the disruption, but the situation was “gradually stabilised” by late afternoon. The Slovak Economy Ministry confirmed that a disturbance had occurred and said it was investigating the incident alongside SEPS.

The European Network of Transmission System Operators for Electricity (ENTSO-E) said it was reviewing the incident in coordination with regional partners but declined to comment on the nature of the disruption or whether it originated within or outside Czech territory.

Blackouts of this scale are rare in the Czech Republic, which has a well-developed energy infrastructure and is typically a net exporter of electricity.

The disruption comes amid increased scrutiny of energy security across the European Union following repeated warnings over ageing grid systems, weather-related stresses and cybersecurity vulnerabilities.

Iberian suffered a large-scale blackout in April when the grid was overloaded by extreme weather. Relying heavily on solar power, the frequencies in the grid were fluctuating too much and caused a cascade of power station shutdowns that plunged most of the region into darkness.