Heavy snow in Stockholm has caused serious delays in train and subway traffic throughout the city since early Friday.

Police said about 25 traffic accidents have been reported since midnight and as many as five people were injured in the mishaps.

"No road was closed, but the whole traffic net became slower," said Ulf Lingren, who is in charge of Stockholm communications.

On Thursday, weather forecasters issued a warning for heavy snow and advised people not to go out if possible because the traffic was in a difficult situation.

In particular, Stockholm train and subway lines above ground faced the greatest difficulty. Almost all bus service was canceled as well.

The weather also caused flight delays. At Stockholm's international Arlanda airport, only one runway was operational as crews worked to remove snow that caused delays of over two hours.