Blast on Volgograd bus kills six

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

The cause of the blast, which happened just after 14:00 local time (10:00 GMT), remains unclear.

Cities further south, in Russia’s North Caucasus, have seen attacks by Islamist militants in recent years; the blast on Monday may be linked.

But it may have been caused by a technical malfunction, reports suggest.