Millions of people have gathered to watch a rare solar eclipse sweep across Europe and plunge countries into darkness.

Crowds in Spain, Iceland and Britain were awed into silence and spontaneous applause by the magical celestial spectacle on Thursday morning (AEDT).

Spain and Iceland had a total solar eclipse while in Britain about 90 per cent of the sun was covered by the moon.

Spectators donned special glasses to view the breathtaking event, their eyes turned skyward, waiting for the moment the sun, moon and Earth aligned.

The moon blocks the sun over Montesinho Natural Park in Portugal. Photo: AAP

Northern and central Spain enjoyed some of mainland Europe’s best views of the show, which began at about sunset local time.

It was reportedly the first time since 1905 that mainland Spain could see this phenomenon, but the next one will be next August.

Different stages of the solar eclipse over Portugal. Photo: AAP

Parts of the Iberian Peninsula plus slivers of Greenland and Iceland went dark during totality — when the moon completely covered the sun’s light for about 2½ minutes.

The eclipse was predicted to reach its maximum duration off Iceland’s west coast.

By the time it reached a small patch of Portugal and then Spain, totality would have dwindled to a minute or so.

The spectacle would then end over the Mediterranean.

People gather at Riegrovy Sady Park in Prague, Czech Republic. Photo: AAP

Rooms in Reykjavík, Iceland’s capital, were averaging more than $1400 for Wednesday night as Icelanders prepared for their first total solar eclipse since 1954 and the first visible from the capital since 1433.

Authorities in the country of fewer than 400,000 people expected up to 20,000 additional overseas visitors for the eclipse, which comes during an already busy peak tourist period.

The moon partially covers the sun over the sea in Vela Luka, Croatia. Photo: AAP

Eclipse glasses were essential for safe viewing. They are made with special filters that block solar radiation that can damage the eyes.

For months, supermarkets, department stores, museums and planetariums across Spain have sold or distributed eclipse glasses, with many pharmacies running out of stock.

The sequence of a total solar eclipse over central Spain. Photo: AAP

The event coincided with a scorching summer of wildfires in Spain, leading to officials rolling out a large public safety campaign.

Spain’s interior ministry said 350 official viewing sites were set up across the country’s sparsely populated interior, an area often referred to as “Empty Spain”.

Authorities limited or restricted access to another 123 sites because of environmental conditions or obstacles that could hinder an evacuation in the event of a wildfire.

An Airbus A321 approaches Berlin Brandenburg Airport during the partial solar eclipse. Photo: AAP

Only weeks ago, the most destructive wildfire in Spanish history devoured 500 square kilometres and forced the evacuation of tens of thousands of people in central Spain.

Several smaller wildfires remain active elsewhere in the country.

Visitors walk along a cliff above Ajo Beach in Cantabria, Spain, after the total eclipse. Photo: AAP

Much of Spain was on alert on Wednesday (local time) as temperatures climbed above 35 degrees and vegetation remained bone-dry.

The national weather agency, AEMET, forecast such temperatures across north-west to south-eastern Spain, including many areas where the total eclipse was to be observed.

-with AAP