The death toll from Monday 29 March's terrorist attacks on the Moscow Metro has risen to 39, with a further 70 injured.
Security on the underground system has been increased, as have the measures at airports.
America has followed suit by doubling patrols on subway stations amid fears the country could be next.
A service in Moscow was running again by 5pm Monday evening with damage to the stations minimal, according to government officials.
It is as yet unclear how many of the usual 5.5 million passengers a day will feel safe enough to use the metro system again.
The attack has drawn universal condemnation from across the globe.
European Council president Herman Van Rompuy said he was deeply shocked by this act of cowardice, for which there was no justification.
"I want to convey my most sincere condolences to the families of the victims and my wishes of prompt recovery to those who were injured," Rompuy said.
Russia's intelligence service the Federal Security Service said investigators believed terrorist groups linked to North Caucasus were behind the attacks.
Russian President Dimtry Medvedev said "We will find and destroy them all."
The attacks happened during the Monday morning rush hour, with the first bomb detonating at Lubyanka Station at just before 8am and a second at Park Kultury Station 40 minutes later.
