At least five people have been killed and more than 100 injured in lightning strikes during a thunderstorm in mountains in southern Poland, and neighbouring Slovakia.

Witnesses say the thunderstorm came suddenly on a day that began with clear weather.

The worst bolt struck a group of hikers at the summit of Giewont, a popular peak in the Tatra range in Poland’s south. Four of the group died.

Two of the victims were children, Polish air ambulance service spokeswoman Kinga Czerwinska told news broadcaster TVN24.

The fifth person was killed in neighbouring Slovakia. The Slovak rescue service said a Czech tourist fell hundreds of metres down the side of a mountain and was killed after lightning knocked him off Banikov peak.

#Zakopane: Several people are reported to have been killed in lightning strikes at the peak of Giewont and other Tatra locations. Multiple ambulance helicopters have been dispatched. – TVN24/Radio ZET
pic.twitter.com/skyJzQNELa

— I.E.N. (@BreakingIEN) August 22, 2019

Rescuers with the Polish Tatra emergency service (TOPR) said they thought the lightning probably hit metal chains that help tourists climb the 1894-metre Giewont peak, or the metal cross on its summit.

“We heard that after [the] lightning struck, people fell. The current then continued along the chains securing the ascent, striking everyone along the way. It looked bad,” Polish mountain rescue service chief Jan Krzysztof told the country’s PAP news agency.

The lightning struck a group of tourists near the summit of the mountain. Photo: AAP

Some of the injured were flown to a hospital in the Polish mountain resort of Zakopane.

Krakow province governor Piotr Cwik said the death toll might rise.

Prime Minister Mateusz Morawiecki, who went to Zakopane, said some of the more than 100 injured were in serious conditions with severe burns or head injuries. They had fallen after being hit by the lightning, or had been hit by falling rocks.

“Nobody expected such a sudden storm to break out and from our human point of view it was something which was impossible to predict,” he told an emergency meeting.

The Tatras, part of the Carpathian mountain range, are the highest mountains in Poland and Slovakia and attract tourists from near and far with scenic lakes and peaks.

Thursday’s lightning strikes were the worst accident in the Tatras since August 1937, when lighting killed four people on Giewont.

-with AAP