HELSINKI (AP) — Swedish police say they are investigating major cyber attacks against some of the country's leading media companies.

Police spokesman Anders Ahlqvist says investigators are unsure about the extent of the denial of service attacks on Saturday but were working closely with security police on the probe. He said some attacks appeared to last for several hours.

Swedish news agency TT reported that hackers hit about a dozen media outlets, including websites of the the main dailies and tabloids.

Ahlqvist said Sunday that some of the IP addresses used by hackers were Russian but that "doesn't mean Russian operators were behind them."