A major disruption in Spain's telecommunications infrastructure early on Tuesday affected emergency response systems and business operations nationwide, the second significant utility failure to hit the country in recent weeks.

The telecom outage, triggered by a planned network upgrade at provider Telefonica, primarily affected fixed-line services, including the internet. It also disrupted voice communications across multiple regions.

The incident left several regional emergency services unreachable, forcing local authorities to establish alternative contact numbers for essential public safety operations.

The telecoms giant described the disruption as affecting only "specific services".

The system failure impacted the 112 emergency phone number in regions such as Andalusia, Aragon, La Rioja, the Basque Country, Galicia and the Valencian Community, said Telefonica.

The telecom network failure impacted multiple providers, and led to widespread connectivity issues across major cities like Madrid, Barcelona, Valencia and Seville, according to trade news website TechInformed.

According to Downdetector, a real-time monitoring platform that tracks service disruption, around 72 percent of complaints on Tuesday morning involved fixed internet services, followed by signal loss and complete outages, as reported by Spanish newspaper El Pais.

Telecom services were fully restored later in the morning following the outages. This was the region's second major infrastructure disruption following last month's power blackout that affected essential services across Spain and Portugal.

The major power outage on April 28 was attributed to high-voltage grid malfunctions, and raised critical questions regarding the resilience of vital utility networks across the Iberian Peninsula.

The power disruption lasted almost 23 hours, affecting essential services — from traffic signals and public transportation to electronic payment systems and aviation operations.

Spanish authorities have initiated formal investigations into the power outage incident, enlisting security agencies and technical specialists, and a high court judge is examining potential cyberattack connections to the blackout.

Spain's Prime Minister Pedro Sanchez and national power grid chief Beatriz Corredor have rejected claims linking the incident to Spain's growing dependence on renewable energy.