DHAKA: An explosion has ripped through a bus in the southern Russian city of Volgograd, killing at least four people and injuring seven.

The cause of the blast is not yet known, Russian officials say, reports the BBC.

Cities further south, in Russia’s North Caucasus, have seen attacks by Islamist militants in recent years.

There may be fears of a link with the Volgograd blast, correspondents say. Another possibility is that a gas canister exploded on the bus.

BDST: 1750 HRS, OCT 21, 2013
RoR/GCP