Second Volgograd attack

Russian officials have raised the death toll from a bomb attack on a trolleybus in the southern Russian city of Volgograd to 14, and suggested that the blast may be linked with Sunday's deadly explosion at the city's main railway station.

Reports said Monday's trolleybus blast completely destroyed the vehicle, a common form of transport in Russian cities, and broke windows in nearby buildings.

A health ministry spokesman said 28 were also wounded in the explosion.

The trolleybus attack comes a day after a suspected suicide bombing at Volgograd's main railway station killed at least 17 people. The death toll rose from 16 overnight when one of the people injured in the attack died of his wounds, hospital officials said.

Investigative Committee spokesman Vladimir Markin said in a statement that the bombs used in both attacks were similar, showing that the two incidents could be linked.

Sochi security fears

The attacks come amid heightened concerns about security for the Winter Olympic Games to be held in the Russian Black Sea resort of Sochi in just six weeks' time.

Sochi is in direct proximity to the volatile North Caucasus region, which sees almost daily violence in the course of an Islamist insurgency.

Although no group has immediately claimed responsibility for the Volgograd attacks, there has been much speculation that Islamist militants active in the North Caucasus region may be behind such attacks, after their leader, Chechen warlord Doku Umarov, called on supporters in July to "do their utmost to derail" the Games.

Monday's attack is the third such attack in Volgograd in two months. In October, six people were killed in a suicide bombing on a bus.

Russia's interior ministry said on Sunday it was stepping up security at all the country's main train stations and airports.

tj/msh (AFP, Reuters, dpa)