Russian President Vladimir Putin has made a visit to Volgograd in the wake of this week's bombings that killed dozens of people in the southern city.
Speaking on January 1, Putin described the Volgograd attacks as an "abomination."
"Whatever motivated the criminals' actions, there's no justification for committing crimes against civilians, especially against women and children," he said.
Putin met with some of the survivors of this week's attacks on Volgograd transport targets. He also met security officials investigating the attacks.
On December 29 a suicide bomber targeted the city's railway station, while another suicide bomber attacked a city trolleybus on December 30. The attacks killed at least 34 people and injured more than 70.
Earlier, in a New Year's Eve address in the eastern city of Khabarovsk on December 31, Putin vowed
to eliminate terrorists in Russia.
"Dear friends, we bow our heads before the victims of the terrible terrorist attacks. I am confident that we will fiercely and consistently continue the fight against terrorists until their total destruction," he said.
He also called the terrorist attacks, along with flooding in Russia's east, the country's two greatest challenges of the past year.
In response to this week's attacks, Russian authorities have placed some 5,200 police and Interior Ministry troops on the streets and on public transport in Volgograd.
Volgograd Governor Sergei Bozhenov said volunteers were helping the police.
"Yes, we do today have Cossack volunteers who, together with police, are patrolling the streets," Bozhenov said. "The number of Cossack volunteers is increasing."
Governments and international organizations around the world have condemned the attacks, including U.S. State Department spokeswoman Marie Harf.
"We condemn in the strongest terms the terrorist attacks in Volgograd," Harf said. "We send our sincere condolences to the families of the victims and stand in solidarity with the Russian people against terrorism of any kind."
The attacks have raised security concerns
ahead of the Winter Olympic Games, which are due to open in the southern Russian city of Sochi, some 700 kilometers southeast of Volgograd, on February 7.
With reporting by AP, AFP, Reuters, dpa, and ITAR-TASS