Russian security services locked down part of a Siberian city on Friday evening in what they said was an operation against a suspected Isis terror cell.

Police in Tyumen (population 670,000) cordoned off several streets to the west of the city centre, evacuating residents and cutting off electricity and street lighting.

Dramatic footage posted on social media shows dozens of armoured vehicles streaming the neighbouring streets.

In a brief statement, the local branch of the FSB said they had received information a group of terrorists had been planning an attack from one of the private houses in the area.

The official statement carried no other details, but Russian news agencies later quoted security sources reporting all of the suspected terrorists had been killed "following armed resistance."

This was the third suspected terror incident in the four months to strike the western Siberia region of Russia. Authorities have previously been accused of covering up the extent of the terror threat in the region.

On 31 December in nearby Magnitogorsk, for example, 39 people died after an explosion caused part of a multi-storey apartment block to collapse.