Terrorists' new weapon of choice - vehicles

The scene of an incident in Drottninggatan, a street in the centre of Stockholm
The scene of an incident in Drottninggatan, a street in the centre of Stockholm

It was a scene which has become disturbingly familiar in recent months.

And while Swedish detectives pick over the clues from the aftermath of the Stockholm shopping district attack, a number of similarities have already been identified.

There are potentially many casualties.

The apparent weapon of choice - a truck - has emerged as a common feature of terror attacks, designed to maximise the number of people killed and seriously injured.

And the location - a busy shopping area in a European capital city - was also expected to have been teeming with people, meaning a higher likelihood of multiple victims.

Detectives will now move to identify the suspect and any conspirators, as well as the motive.

Islamic State (IS) has previously called on its supporters for vehicular-based attacks in crowded areas, although it has yet to claim responsibility for the Stockholm incident.

The Nice terror attack, on July 14 last year, was among the most high profile in recent years.

Some 86 people were killed and more than 400 were injured when 31-year-old Mohamed Lahouaiej Bouhlel drove a hired lorry through crowds gathered to celebrate Bastille Day on the Promenade des Anglais in the south of France.

IS said it was responsible for the attack.

A dozen people were killed, and 48 left injured, when a truck was hijacked and driven at speed by Tunisian terrorist Anis Amri into crowds at a Christmas market in Berlin last year.

Harrowing eyewitness footage from the scene showed the moment the truck careered through the German capital on December 19, sending frantic shoppers scrambling for safety.

Hours after his death, IS released a video claiming to show Amri - who was subsequently shot dead by police while on the run in Milan - pledging allegiance to the extremist group and vowing to avenge militants killed in coalition air strike.

News of the carnage in Stockholm came hours after it was announced a fifth victim had died in the Westminster terror attack that brought violence and bloodshed to the streets of London.

Romanian tourist Andreea Cristea, 31, died in hospital on Thursday when her life support machine was switched off, two weeks after Muslim convert Khalid Masood injured her and scores of others when he ploughed into pedestrians on Westminster Bridge on March 22.

READ MORE: VIDEO: Romanian tourist struck in Westminster attack dies in hospital
Footage from the incident showed Ms Cristea being thrown into the River Thames as the car 52-year-old Masood, from Birmingham, was driving roared across the bridge, destined for the Palace of Westminster.

Ms Cristea's death meant five victims lost their lives as a result of Masood's actions that day.