At least 10 people have been killed and 10 others hurt in a suspected terrorist attack on a trolleybus in the Russian city of Volgograd, officials say.

The blast comes a day after 17 people died in a suicide bombing at the central station in the city.

Security has been tightened at railway stations and airports across Russia.

Moscow is concerned militant groups could be ramping up violence in the run-up to the 2014 winter Olympic Games in the city of Sochi.

The Olympic venue is close to Russia's volatile north Caucasus region.

Volgograd lies about 900km (560 miles) south of Moscow, 650km north of the North Caucasus and 700km north-east of Sochi.

The latest explosion took place near a market in the city's Dzerzhinsky district on Monday morning.

The area has been cordoned off, and police and emergency services are at the scene.

Images posted on social media websites showed a burned-out vehicle and bodies scattered around.

Sunday's blast rocked Volgograd-1 station at around 12:45 (08:45 GMT) at a time of year when millions of Russians are travelling to celebrate the New Year.

A nearby security camera facing the station caught the moment of the blast, showing a bright orange flash behind the station's main doors.

The explosion shattered windows and sent debris and plumes of smoke from the station entrance.

No group has yet claimed responsibility for the blast, but a spokesman for Russia's Investigative Committee said the incident was being treated as an act of terrorism.

Source: BBC