Russian President Vladimir Putin has signed a decree to tighten security in the Black Sea resort of Sochi during the 2014 Winter Olympics, imposing restrictions on freedom of movement and assembly that critics said violated human rights.

It bars movement into the sprawling city without special permission creating a special 'prohibted zone' for the event. 

Public gatherings "not connected" with the Olympics in high security areas on land and sea are also banned.

Mr Putin has staked his reputation on the security and success of Russia's first post-Soviet Olympics and has ordered law enforcement authorities to stop any attacks by Islamist militants from nearby North Caucasus provinces.

Human rights activists argue the restrictions are draconian.

In early July, militant warlord Doku Umarov revoked a previous order to refrain from attacking Russian targets outside the North Caucasus and urged militants to use "maximum force" to prevent Mr Putin staging the Games. 

Umarov is wanted by Russian authorities for masterminding terrorist attacks killing civilians on the Moscow metro in March 2010 and Domodedovo Airport in 2011. 

Published in the official newspaper Rossiiskaya Gazeta on Friday, the decree enters into force on 7 Jan, a month before the opening ceremony, and expires on 21 March, a month after the Olympics end.

Barring cars from outside Sochi restricts Russians' freedom of movement and the ban on most public gatherings violates their constitutional right to free assembly, said Pavel Chikov, a human rights lawyer and head of the legal aid group Agora.

He told Ekho Moskvy radio such restrictions required passage of a law or imposition of a state of emergency.

"Under such conditions the Olympics, which are supposed to be celebration of sport and democracy, will become the exact opposite," prominent Russian environmental activist Alexei Yablokov said in a comment posted on the Internet.

"Nature is being destroyed, people are being evicted from their homes, and now it turns out that a state of emergency is being imposed," he said.

Gay rights activist Nikolai Alexeyev said he planned to hold a gay pride march in Sochi on the opening day of the Olympics and that it could not be prohibited by presidential decree.

"Are the Olympics an emergency situation, like a war or a natural disaster?" Alexeyev was quoted as saying by the website

"There has been no precedent in history in which peaceful demonstrations have been banned in a city where the Olympics were being held."

A law Mr Putin signed this year banning gay "propaganda" has been criticised by Western governments and prompted calls for a boycott of the Olympics.

Russia has offered assurances that the law will not affect athletes or spectators.

In the decree, Mr Putin said its purpose was the "implementation of increased security measures" called for in a law adopted in 2007, when the Olympics were awarded to Sochi.

Kremlin officials could not immediately be reached for comment on Saturday.