OSLO, July 12 (Xinhua) -- While forest fires, probably caused by lightning, spread in many places in southern and eastern Norway, fire helicopters were hampered by thunderstorms, newspaper Aftenposten reported Thursday.

During the day there have been at least 115 fires reported and it is still unclear how many of these have been put down, the report said.

"It is so dry now that every small thing ignites," Oddbjorn Wikan from the emergency station in the southern municipality of Telemark told public broadcaster NRK.

In the western part of the area, there have been between 100 and 200 phones calls about fires, NRK reported.

"We will activate more helicopters when the thunderstorm is over. There are lightning and thunder in many places, and the helicopters can not fly under such weather conditions," Anders Fevik, press officer from the Norwegian Directorate for Civil Protection (DSB), told Aftenposten.

The cause of the fires is probably lightning, Norwegian police reported on Twitter.

Lightning also caused delayed and cancelled trains due to the power cut.

DSB went earlier this week with a reminder of the extreme forest fire hazard in southern Norway.