The Sun has unleashed four potent solar flares this week, marking the most intense activity yet this year and causing limited interruptions to high-frequency radio communications.

One of them was classified as an X3.2 flare, with X-class flares being the most intense type, the US space agency said.

“This is the strongest X-class flare of 2013 so far, surpassing in strength the two X-class flares that occurred earlier in the 24-hour period,” NASA said of the flare that peaked at 0111 GMT Tuesday.

A fourth X-class flare peaked at 0148 GMT on Wednesday, NASA said.  Measuring at X1.2, it caused a temporary radio blackout that has since subsided, and was categorized as “strong,” or R3 on a scale of 1 to 5 on the National Oceanic and Atmospheric Administration’s space weather scales. The latest flares began on May 13 and have sent off bursts of radiation from the Sun, known as coronal mass ejections (CMEs).