Sweden should take steps to increase security against attacks at its nuclear plants including introducing armed guards, a government-sponsored report published Thursday said.

"A terror attack against a nuclear power plant can have the same consequences for the surroundings as a nuclear power plant accident," the Swedish Radiation Safety Authority said in a statement.

The authority, along with the national police administration, the Swedish National Grid and the Swedish Civil Contingencies Agency, authored the 139-page report, calling for among other things expanding the protection area around the plants and for permanent and armed security forces on-site.

"There is no reason why these security guards should not have the ability to protect themselves if they are exposed to violence. I don't think this is very controversial," Swedish Radiation Safety Authority inspector Stig Isaksson told AFP.

He stressed though that the most important step towards better security was ensuring better coordination between authorities and agencies so they could respond quicker if a threat emerged.

Isaksson said that Swedish security police were unaware of any "concrete threats" in recent years against the Scaninavian country's three nuclear plants and 10 reactors, pointing out that environmental activists had prompted Sweden's centre-right government to commission the report.

In June 2010, 50 Greenpeace activists entered the Forsmark nuclear power plant near Uppsala, north of Stockholm, to protest the reversal of a moratorium on nuclear power.

Twenty-nine of them were later fined for trespassing, with one found guilty of lesser arms law violation for possession of pepper spray.

Among the changes proposed in the report is to tighten laws against trespassing at nuclear facilities and beef up the penalty for doing so.