The death toll from two suicide bombings in the southern Russian city of Volgograd has risen to 33 after two victims succumbed to their injuries, the emergency situations ministry said Tuesday.
"A victim of the explosion at the train station on December 29 died last night in the Volgograd hospital and the number of dead has risen to 18," ministry spokesman Dmitry Ulanov told the Interfax news agency.
He added that another victim of Monday's suicide bombing on a trolleybus had also died, raising the toll from that blast to 15.
President Vladimir Putin has ordered stepped-up security across the country after the trolleybus bombing at the peak of the morning rush and Sunday's suicide attack, which was blamed on a suspected female suicide bomber.
The attacks have heightened security fears around the Sochi Winter Olympics which open on February 7.
Doku Umarov, the leader of militants seeking to impose an Islamist state throughout North Caucasus, has ordered rebels to target civilians outside the region and disrupt the Games.