At least seven people have been killed in an explosion on a bus in the southern Russian city of Togliatti.

More than 20 others were injured by the blast. The governor of the Samara region said the attack was being treated as a "terrorist" act.

Security officials say an explosive device may have been fixed to the vehicle, or carried on board.

It was the second blast on a bus in Russia in just over a week, following an explosion in Dagestan province.

PHOTO CAPTION

Russian national flag.

BBC