Russian President Vladimir Putin signed Friday a controversial new law that increases the maximum fines for protest-related offenses.

"A society which permits rallies and marches must protect itself from radicalism," Putin said, adding that he did not consider the law unnecessarily harsh, as cited by RIA Novosti.

He also said, however, that the law could be amended if judicial officials considered it "necessary."

The law was proposed by deputies from the ruling United Russia party in the wake of clashes between police and demonstrators at a downtown Moscow rally on the eve of Putin's May 7 inauguration as president for a third term. It was then fast-tracked through parliament ahead of another planned June 12 anti-Putin rally in Moscow.

The Kremlin's human rights council said earlier it would ask Putin to veto the law, which has also been criticized by the Parliamentary Assembly of the Council of Europe. Putin's spokesperson Dmitry Peskov has said the law is "in line" with European norms.

"The authorities are fighting against the protests, instead of fighting against the injustice that is causing them," protest movement leader Ilya Yashin told RIA Novosti. "This is an absolutely irresponsible policy that has put Russian on the brink of a civil confrontation."

But Yashin also said he doubted the new fines would scare off protesters.

"We are not easily frightened," he said.

The law, which will come into force after its publication in the Rossiiskaya Gazeta government newspaper on Saturday, raises the maximum fine for participation by private citizens in illegal protests from the current RUB 100 (USD 3) to RUB 10,000 (USD 300).

Those found guilty of a "violation of the established rules of conduct" at protests can now be hit with fines of RUB 20,000, up from the current RUB 1,000. Organizers of protests that result in damage to person or property will face maximum fines of RUB 300,000.

The average monthly salary in Russia is around USD 900, although wages are much higher in Moscow and St Petersburg, the hotbeds of the ongoing protests against Putin's 12-year rule.

Judges can also sentence protesters to 20 to 200 hours of community service, for a maximum of four days a week. The law also bars protesters from wearing masks at rallies and forbids anyone with a criminal record from organizing a demonstration.