Two terror attacks in the southern Russian city of Volgograd earlier this week have heightened security concerns for the upcoming Sochi Winter Olympics, jeopardizing one of Vladimir Putin's most cherished objectives.

By hosting a successful Olympic Games, Putin is hoping to demonstrate to the world that Russia is a modern state, one that controls every corner of its vast land.

But the Russian president chose the most improbable location to host the Winter Games: a snowless resort town surrounded by militants and rebels.

While Volgograd lies 700 kilometres northeast of Sochi, the two cities are essentially neighbours in a hotbed of militancy and terrorism.

Putin has wanted to show that unrest in the Caucasus, at its height during the two Chechen wars in the mid-to-late 1990s, is a thing of the past.

But reality seems to be intruding.

In July, Chechen rebel Doku Umarov — referred to as "Russia's bin Laden" in Russian media — lifted a moratorium on attacks on civilian targets, urging his supporters to use "maximum force" to prevent the Sochi Olympics from taking place.

Umarov heads the Caucasus Emirate, a terrorist organization that fights for a self-proclaimed Islamic state in Russia's southwest, and Sochi lies at the heart of this contested territory.

On Sunday, a man authorities have identified as Pavel Pechyonkin, a 32-year-old paramedic, detonated the equivalent of 10 kilograms of explosives in the main hall of the Volgograd train station filled with New Year's travellers. The attack killed 17 people and injured 45 others.

Russia Putin

Russian President Vladimir Putin gestures while speaking at his annual news conference in Moscow on Dec. 19, 2013. He has repeatedly assured the world that Russia will be safe from terrorist threats during the Sochi Olympics in February. (Ivan Sekretarev / Associated Press)

The very next morning, at rush hour, a tram carrying Volgograd commuters was blown up in front of a busy market, killing 15 people and injuring 23 others.

This was the third terrorist attack to hit the city of one million in the past two months. In October, a Dagestani woman detonated a bomb on a city bus, killing six.

Umarov, who claimed responsibility for the terrorist attacks on the Moscow Metro in 2010 and Moscow's Domodedovo International Airport in 2011, has been reported dead on many occasions.

But Umarov's supporters have heard his message and the Volgograd attacks show that his orders are being executed.

A long history

In Russia, terrorism hits home. During the past decade, Moscow and the Caucasus have witnessed car bombs, suicide attacks and hostage takings.

Heightened security measures had yet to be felt in Moscow as of Monday evening, although metal detectors and policemen scanning the capital's crowds for suspicious people and objects remain common sights.

But the policemen that dot the capital's landscape — in train and metro stations, major shopping malls and concert halls — remind Muscovites that their commute and daily activities are always a bit risky.

Attacks on Volgograd, a "soft target" according to analysts, might suggest that security forces have succeeded in keeping terrorism out of Russia's more strategic and populous sites since the bomb attack on Moscow's Domodedovo Airport 2011, which killed almost 40 people

But like many things in Russia, security is negotiable; there are often ways to get around it.

Unattended baggage — two words that would trigger an immediate response from a North American anti-bomb squad — is commonplace in the country's airports.

Moscow's metro attendants, who sit in cramped booths at the bottom of escalators, are paid 25,000 rubles a month ($810) to watch for safety violations and suspicious behaviour. But the dour-faced women often read paperbacks or do crosswords.

Putin repeatedly has assured the world that the Sochi Games will be safe. The International Olympic Committee also said it was "confident" that Sochi would be "safe and secure."

But this week's double bombings challenge those assertions.

'All necessary measures'

In response to the Volgograd attacks, Putin ordered law enforcement agencies and the country's National Anti-Terrorism Committee to take "all necessary measures" to curb terrorism.

On Monday, the Russian Minister of Interior reported that security forces had killed "a few terrorists" in the country's south on Sunday night and that security measures would be heightened at transportation hubs.

Doku-umarov

Dead or alive? It's not clear. But Chechen Islamist Doku Umarov, referred to as "Russia's bin Laden" in the Russian media, is still being listened to. (Associated Press)

More than 4,000 policemen were deployed to Volgograd on Monday to take part in an anti-terrorism operation, in which 87 people have already been detained.

Volgograd authorities have cancelled all New Year celebrations and declared five days of mourning.

Patriarch Kirill, the head of the Russian Orthodox Church, said that the citizens of the "hero city" formerly known as Stalingrad could not be frightened by these evil acts.

But for now, city officials have said that residents are panicked. Commuters reportedly have avoided public transportation, fearing further attacks.