A spectacular auroras could be spotted over Russia, Ukraine, Germany, Slovenia, Britain and other parts of Europe as most powerful solar storm in more than two decades struck Earth on Friday.

It was later upgraded to an “extreme” geomagnetic storm — the first since the so-called “Halloween Storms” of October 2003 caused blackouts in Sweden and damaged power infrastructure in South Africa.

The agency said several other coronal mass ejections (CMEs) are expected to hit Earth in coming days.

Netizens posted pictures of auroras from northern Europe and Australasia.

Meanwhile, authorities notified satellite operators, airlines and the power grid to take precautionary steps for potential disruptions caused by changes to Earth’s magnetic field.

Unlike solar flares, which travel at the speed of light and reach Earth in around eight minutes, CMEs travel at a more sedate pace, with officials putting the current average at 800 kilometers (500 miles) per second.

They emanated from a massive sunspot cluster that is 17 times wider than our planet. The Sun is approaching the peak of an 11-year cycle that brings heightened activity.

A  professor of space physics Mathew Owens told AFP that while the effects would be largely felt over the planet’s northern and southern latitudes, how far they would extend would depend on the storm’s final strength.

“Go outside tonight and look would be my advice because if you see the aurora, it’s quite a spectacular thing,” he added. If people have eclipse glasses, they can also look for the sunspot cluster during the day.