Russia’s Fast Payment System (FPS) suffered a major disruption on Thursday, causing widespread transaction delays and sparking thousands of user complaints, according to data from monitoring services Downdetector and Sboy.rf.

The outage began around 4 p.m. Moscow time, with nearly 4,500 incident reports filed within a single hour. Most complaints came from users in Moscow and St. Petersburg, who reported being unable to complete instant money transfers through the FPS platform.

The disruption of the Central Bank-operated FPS also affected key financial services, including those of Sberbank, T-Bank, Ozon Bank and Yandex Pay.

The National Payment Card System (NPCS), a division of the Central Bank that oversees the FPS, confirmed the outage and attributed it to an unspecified “incident” involving one of its service providers.

“The system is experiencing delays in transaction processing. Further information will be provided once services return to normal,” NPCS said in a statement.

This spring, at least three separate disruptions were reported over a two-week period in late March and early April. During those incidents, users also experienced problems with mobile apps and payment processing.

State communications watchdog Roskomnadzor later confirmed the latest FPS failure and its cascading effects on affiliated services. However, the agency said no evidence of a distributed denial-of-service (DDoS) cyberattack had been found on the payment system’s infrastructure.