MOSCOW – Russian forces went on combat alert in Sochi and tightened restrictions on access to the Black Sea resort on Tuesday as part of measures by President Vladimir Putin to ensure security at next month's Winter Olympics.

Aware that the success or failure of the Sochi Games will help shape his legacy, Putin has increased security in Russia following two suicide bomb attacks in the southern city of Volgograd which killed at least 34 people.

Moscow's most wanted man, the Chechen insurgent leader Doku Umarov, has urged militants who want to carve an Islamic state in Russia's south to use "maximum force" to prevent the Games going ahead.

"From January 7, all divisions responsible for ensuring the security of guests and participants at the Games are being put on combat alert," Emergency Situations Minister Vladimir Puchkov was quoted as saying by Itar-Tass news agency.

"All security issues for the Winter Olympics are being dealt with at the highest international level."

Authorities are deploying tens of thousands of police and interior ministry troops to Sochi, where athletes will compete for more than two weeks in the most expensive Olympics from Feb. 7.

From Tuesday, which was Russian Orthodox Christmas, access was being further curtailed into Sochi, where a new traffic scheme has come into operation to give priority to Olympic transport, officials said.

"The restrictions are to make the roads free and easy for spectators, athletes and members of the Olympic family to move around," a transport directorate said.

The security measures have prompted complaints from locals, whose city has been transformed from a former Soviet-era seaside resort into a metal-and-steel metropolis.

More than 200 people protested against how Moscow has run the Games so far on Sunday, under the banner of: "Natives of Sochi own the Games, not the visitors."

But Putin, who on Saturday attended a rehearsal of the Games' opening ceremony in Sochi, has eased curbs on demonstrations, allowing groups to hold some marches and gathering at sites approved by the security services.

Campaign groups, calling for everything from gay rights to political reform, have complained that the ban on rallies, imposed in August as part of earlier security measures, violated the Russian constitution.